| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Structural Biology Unit, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110 067, India
Reprint requests to: Dinakar M. Salunke, Structural Biology Unit, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110 067, India; e-mail: dinakar{at}nii.res.in; fax: 91-11-616-2125.
(RECEIVED April 18, 2002; FINAL REVISION June 10, 2002; ACCEPTED June 13, 2002)
Article and publication are at http://www.proteinscience.org/cgi/doi/10.1110/ps.0211602.
 |
Abstract |
|---|
 TOP Abstract IntroductionResults and DiscussionConclusionMaterials and methodsReferences |
|---|
Keywords: Indolicidin; antibacterial peptide; retro; endotoxin; plasticity of molecular interactions; primitive host defense
Abbreviations: LPS, lipopolysaccharide • retro, peptide sequence with amino acids in reverse order • inverso (D-analog), peptide sequence with amino acids consisting of opposite-handedness • retro-inverso, peptide sequence with amino acids consisting of opposite-handedness in reverse order
|
Introduction |
|---|
|
TOPAbstractIntroductionResults and DiscussionConclusionMaterials and methodsReferences |
|---|
A major component of the mammalian innate immunity constitutes expression of a large number of multifunctional proteinaceous effector molecules by neutrophils, which work as antibiotics after they are posttranslationally processed (Gudmundsson and Agerberth 1999). The molecular mechanisms associated with these antibiotics are expected to be relatively simple because the primary objective is to appropriately target and kill the pathogen. A diverse array of mechanisms by which peptidyl antibiotics attack the bacterial cell have been proposed. They include formation of a leakage channel across the membrane (Boman 1991), clustering at the membrane surface causing co-operative permeabilization by the carpet effect (Shai 1995), receptor-activated non-pore-forming mechanisms involving stereospecificity (Casteels and Tempst 1994), and inhibition of protein and DNA synthesis (Boman et al. 1993). The observed differences in the mechanisms of bacterial killing by peptidyl antibiotics appear to be consistent with the structural diversity among these molecules. In addition to their antibacterial activities, these molecules appear to be capable of performing several functions, such as endotoxin neutralization (Larrick et al. 1994), inhibition of tissue-degrading enzymes (Gao et al. 2000), and promotion of wound healing (Gallo et al. 1994), which are all indirectly related to the protection of the host.
We had earlier analyzed the mechanism of activation of tritrypticin (VRRFPWWWPFLRR), a cationic antibacterial peptide derived from a member of the cathelicidin precursor family (Zanetti et al. 1995; Nagpal et al. 1999). Cathelicidins belong to a larger family of cationic antibacterial peptides having two distinguishing structural features: amphipathicity and a net positive charge of at least 2 (Hancock 1997). They vary in length—from 13 to 30 residues—and show diverse sequences. The initial event common to all the cationic peptides appears to be the binding of the positively charged residues of the peptide to the negatively charged molecules exposed at the target cell surface, before permeabilization and bacterial killing (Hancock et al. 1995). We had suggested that tritrypticin undergoes a conformational transition while approaching the membrane receptor (Nagpal et al. 1999). Another cationic peptide, indolicidin (ILPWKWPWWPWRR-NH2), which is also a processed antibacterial peptide obtained from its corresponding precursor protein of the cathelicidin family appears to be functionally similar to tritrypticin (Selsted et al. 1992; Zanetti et al. 1995; Nagpal et al. 1999). The correlation of sequence homology and functional properties of indolicidin and tritrypticin led us to design a retro-analog of indolicidin. Comparison of structure–activity profiles of native and retro-indolicidin shed light on the molecular specificity in the context of primitive host defense.
|
Results and Discussion |
|---|
|
TOPAbstractIntroductionResults and DiscussionConclusionMaterials and methodsReferences |
|---|
). Three different functional attributes were used for this comparison: antibacterial activity, effect of divalent cations on the antibacterial activity, and the ability to competitively displace polymyxin B from endotoxin binding.
|
). The dose-dependent increase in the antibacterial activities of both peptides was evident, although indolicidin shows lower activity than Sym11. The control, 12mer peptide (DVWYPYPYASGS), showed no activity.
Measurement of the antibacterial activity assayed as a function of divalent cations also represents a functional measure of the cationic antibacterial peptides because they bind to the anionic sites on the membrane surface as an initial event (Hancock 1997). The effect of MgCl2 on antibacterial activities of these two peptides against S. typhimurium (Fig. 1B) yields IC50 of 55 mM for Sym11 and 6 mM for indolicidin. Thus, MgCl2 can displace indolicidin more easily than Sym11 from the bacterial membrane, which is consistent with the observation that the latter has higher antibacterial activity than former.
Neutralization of LPS, which is also referred to as endotoxin, by indolicidin has been suggested earlier (Falla et al. 1996). Polymyxin B, a potent drug for endotoxin shock, is known to bind and effectively neutralize septic shock activities of LPS. It has been shown that indolicidin can displace polymyxin B competitively. The endotoxin binding of Sym11 and indolicidin were compared using in vitro polymyxin B displacement assay (Moore et al. 1986), as shown in Figure 1C. It was observed that both the peptides could displace polymyxin B from endotoxin with IC50 of 18 µM and 17 µM for indolicidin and Sym11, respectively. Thus, the ability of Sym11 to displace polymyxin B from endotoxin is similar to that of indolicidin.
It is evident that the overall activity profiles of indolicidin and Sym11 are very similar in terms of different functional properties. The Sym11 analog shows better activity compared to indolicidin in the majority of the assays. This is not surprising considering that Sym11 incorporates both NT7 (RRFPWWW) and CT7 (WWWPFRR), which were independently adequate for exhibiting antibacterial activity (Nagpal et al.1999), whereas indolicidin shows similarity only with the C-terminal region of Sym11 (Fig. 1D).
Functional behavior of retro-indolicidin is identical to that of native indolicidin
The homology of indolicidin with the C-terminal region of Sym11 (Fig. 1D), combined with the fact that Sym11 is symmetric, indicates that the retro-analog of indolicidin (RRWPWWPWKWPLI-NH2) would also be homologous to the N-terminal region of Sym11, as seen in Figure 1D. On the basis of this logic, it can be anticipated that retro-indolicidin may show functional behavior similar to native indolicidin in terms of various activity features.
The antibacterial activity of retro-indolicidin was determined against gram-negative, as well as gram-positive, bacteria. Comparison of the antibacterial activity of the two peptides against S. typhimurium shows a dose-dependent increase in the activity of retro-indolicidin, which was practically identical to that in the case of the native peptide (Fig. 2A). Comparison of the activities, by radial diffusion assay, of the two peptides against Escherichia coli and Streptococcus group A also showed similar behavior (data not shown).
|
). The IC50 values of 9 mM and 6 mM were observed in the case of retro-indolicidin and indolicidin, respectively. Thus, the divalent cation can displace both of the peptides with comparable efficiency from the bacterial membrane.
The functionally relevant binding of polymyxin B to endotoxin is highly specific. The competitive displacement of polymyxin B from endotoxin by retro-peptide was analyzed and compared with that of the native indolicidin (Fig. 2C). It was observed that the retro-indolicidin could displace polymyxin B from endotoxin with an IC50 value of 17.5 µM. This is comparable to that of native indolicidin.
Thus, indolicidin and retro-indolicidin both show remarkable similarity in terms of various traits of activity. The observation that the retro-peptide shows a similar activity profile as that of the native peptide at a variety of different levels is intriguing. Similarity in activity of retro- and native peptides has been observed in a few other instances as well (Merrifield et al. 1995; Ido et al.1997; Pinilla et al. 1998; Vunnam et al. 1998). It was anticipated that the functional correlation between indolicidin and its retro-analog has adequate molecular basis. Diverse manifestations of activity used for comparing native indolicidin and its retro-analog shown above provide indirect functional correlation at the molecular level. To assess if functional similarities would reflect at the structural level as well, it was pertinent to analyze the direct structural interactions between indolicidin and the corresponding receptor, which is LPS in this case.
Model of the indolicidin–endotoxin binding
Availability of the experimentally determined three-dimensional structures of indolicidin and endotoxin enabled us to model the interaction between the two molecules in a knowledge-based manner. The solution structure of indolicidin in lipid-like medium has recently been determined (Rozek et al. 2000). Also the crystal structure of a complex of LPS with an LPS-binding protein, FhuA from E. coli, has been determined (Ferguson et al. 2000). Using these two structures, we have modeled the interaction of indolicidin with LPS. The indolicidin molecule was docked in the LPS structure using the ligand-interacting residues and stereochemistry of the LPS-binding protein as the guide. This was followed by energy minimization of the complex. The intermolecular energy was calculated to be -95.41 Kcal/mole. The energy-optimized model of the indolicidin-LPS complex is shown in Figure 3. It was observed that the two arginine residues at the N terminus of indolicidin exhibit ionic interactions with the phosphates of the LPS such that the guanidyl group of Arg 12 makes two hydrogen bonds with O6 of the diphosphate and that of the Arg 13 forms a hydrogen bond with O2 of the phosphate in LPS. The hydrophobic residues of the peptide—constituted by the three tryptophan residues—interact with the hydrophobic fatty acid tails of the LPS, which essentially wrap around this part of the peptide.
|
The direct affinity measurements of the LPS binding with indolicidin were consistent with the observed structural features in the above model. The anti-endotoxin activity of indolicidin assayed by polymyxin B displacement from LPS can be directly probed using an affinity biosensor and correlated with the direct interactions between the LPS and the peptide. Binding of indolicidin to immobilized LPS was assayed by IAsys Auto Plus. Figure 4A shows the sensograms of the interaction of indolicidin with LPS at different concentrations. It is apparent that the LPS–indolicidin binding, with the KD value of 45.2 µM, is favorable. The low value of the dissociation constant correlates well with the nature of the binding interactions of the indolicidin to LPS, mediated by salt bridges and hydrophobic interactions, as described in the structural model.
|
). It is evident that the KD value of retro-peptide, calculated on the basis of the sensograms, was almost identical (43.6 µM) to that of the native peptide. The Kon and the Koff values were also comparable for the two peptides (Table 1) indicating that the kinetics of binding are also similar in the two cases. This implies that the nature of interactions involved in the binding of the retro-peptide to the LPS is similar to that involving the native peptide. This would necessitate similarity of structures between indolicidin and its retro-analog. It is intriguing how a retro-sequence corresponding to a bioactive peptide will resemble its native counterpart.
|
). In aqueous solution, the CD spectra of indolicidin, as well as retro-indolicidin, are characterized by a broad negative band at 200 nm. Both the peptides also show a positive band at 228 nm, which has been attributed to the conformational propensities of tryptophan side chains of indolicidin (Woody 1985). A transition from a small positive to a significant negative band at 228 nm is evident on LPS binding, indicating reorientation of the tryptophans. The negative band at 228 nm on LPS binding can be attributed to the constrained conformations of tryptophan residues while interacting with the fatty acid region of LPS (Fig. 3), similar to that observed in the tritrypticin analogs having ß-turn conformation constrained through intramolecular interactions (Nagpal et al 1999).
|
) and consistent with the secondary structural propensities. The CD profiles of indolicidin and retro-indolicidin bound to LPS also show remarkable similarity. This functional and structural equivalence should be manifested in the interaction of the retro-peptide with LPS. It is evident from the model above that indolicidin binds to LPS through ionic and hydrophobic interactions. It should be possible to juxtapose the retro-peptide with LPS, such that its interactions mimic the native indolicidin. The long side chains of arginine residues and the relatively bulky head group of LPS provide significant flexibility so that the ionic interactions are optimized irrespective of the orientation in which the peptide is presented. Similar optimization opportunities exist for hydrophobic interactions around the tryptophan residues due to the flexibility of the fatty acid chains. Therefore, the most likely mode of recognition of receptors by indolicidin or the retro-peptide could be through a dumbbell-shaped structure with hydrophobic residues clustered on one side and the ionic residues clustered on the other. In such a structure, the hydrophobic cluster and the cationic cluster of residues would be positioned appropriately at a specific distance, such that they complement the structural features while binding to the corresponding receptor on the membrane surface. Such a model gives enormous leeway, in terms of structural design, of specifically presenting the peptides to the receptor.
If reversal of the sequence does not have any problem in terms of achieving the functionally acceptable topology, inversion of the sequence (changing the handedness) should also be able to retain the functional topology. To test this hypothesis, we have analyzed antibacterial activities of the D-analogs (inverso) of indolicidin and retro-indolicidin against S. typhimurium by radial diffusion assay in a dose-dependent manner. As shown in Figure 6, both of them show similar activities. Thus, as expected, the antibacterial activities of the D-analogs were also comparable to their L-counterparts.
|
|
Conclusion |
|---|
|
TOPAbstractIntroductionResults and DiscussionConclusionMaterials and methodsReferences |
|---|
Thus, the key to the interaction between the cationic antibacterial peptides and LPS, as also inferred from their antibacterial activity, is the plasticity of molecular interactions. This form of plasticity has been shown to be a functional requirement in many instances (Keenan et al. 1998; Chen and Sigler 1999; Stock et al. 1999; Manivel et al. 2000). In the case of indolicidin, in which the binding affinities are very much in the physiological range, plasticity may be linked to the recognition of gross submolecular patterns, an issue that might have been of critical significance for a primitive form of host defense. The conformational flexibility associated with the residues of indolicidin and the fatty acid chains of LPS contribute to the plasticity of binding. Plasticity of interactions also ensures the recognition of a broad spectrum of organisms, which would be a necessity in primitive host defense.
|
Materials and methods |
|---|
|
TOPAbstractIntroductionResults and DiscussionConclusionMaterials and methodsReferences |
|---|
The gram-negative bacterial strains S. typhimurium 3261 PNP2 Gro A mutant and E. coli BL21 (
D3) and Streptococcus group A were used for radial diffusion assay. Agarose I (biotechnology grade) was obtained from Amresco and tryptic soy broth (TSB) was from Himedia Laboratories.
Peptide synthesis, purification, and characterization
Indolicidin, tritrypticin, and their analogs were synthesized by solid phase method using an automated peptide synthesizer, model 431A from Applied Biosystems, Inc., employing standard Fmoc methodology. The peptides were cleaved from the resin by treatment with TFA/thioanisole/phenol/water/EDT in the ratio as recommended by Applied Biosystems, Inc. The crude peptides were purified using a C-18 column (Deltapak, 100 Å, 15 µ, spherical, 19 x 300 mm, Waters) and peptide purity was verified using a C-18 analytical column (Deltapak, 300 Å, 15 µ, spherical, 7.8 x 300 mm, Waters). Characterization was performed by molecular mass determination using a single Quadruple mass analyzer (Fisons Instruments).
Antibacterial assay
The radial diffusion assay was performed using double-layered agarose as described previously (Nagpal et al. 1999).
Effect of cation on antibacterial activity
Indolicidin, retro-indolicidin and Sym11 were tested for their antibiotic activity against S. typhimurium in the presence of MgCl2 by radial diffusion assay. Different concentrations of MgCl2 were mixed with the underlayer agar composed of 1% agarose, 0.03% TSB, and 0.02% tween 20 in 10 mM PB at pH 7.4, which is inoculated with 
1 million bacterial cells. This mixture was poured into a round petri plate; 5 µL of 1 mM peptide in triplicate was added in each well made in the underlayer. The plates were incubated for 3 h at 37°C. The overlay agar containing 1% agarose in 10 mM phosphate buffer at pH 7.4 and 3% TSB was then poured over it and further incubated at 37°C for 18 to 24 h. The diameter of the clear zone surrounding the wells was measured. The inhibition zone obtained with peptide in the absence of cation was considered as 100% antibacterial activity.
Dansyl polymyxin B displacement assay
Dansyl polymyxin B, a fluorescent derivative of polymyxin B, was prepared by condensing polymyxin B sulphate with dansyl chloride as described by Schindler and Teuber (1975). The comparative binding affinity of various antibiotic peptides for endotoxin were investigated by dansyl polymyxin B displacement assay (Moore et al. 1986). The data was expressed as the percent dansyl polymyxin B bound to the endotoxin as a function of peptide concentration. The sample concentration resulting in 50% displacement (IC50) of dansyl polymyxin B was thus determined from the graph.
Endotoxin binding
Binding kinetics were determined by using IAsys Auto Plus, Affinity Sensor. LPS was biotinylated with NHS-LC-biotin as described by de Haas et al. (1998). Biotinylated LPS pretreated with EDTA and sodium-desoxycholate as reported earlier (de Haas et al. 1998) was immobilized onto a streptavidin bound on a biotin-coated surface at a concentration of 0.25 mg/mL in 10 mM phosphate buffer saline at pH 7.4. Approximately 600 arc sec of endotoxin were immobilized (600 arc sec corresponds to an immobilized protein concentration of 1 ng/mm2). The unreacted sites were blocked with d-biotin. All measurements were carried in 10 mM HANK'S balanced salt solution. For the determination of association rate constants, the antibiotic peptides (100 µM–6.25 µM) in the same buffer were used. Dissociation rate constants were measured by replacing the sample by buffer. Following analyte binding, the surface was regenerated with 10 mM GlyHCl at pH 2. Kinetics of the interaction of the peptides with endotoxin were analyzed by nonlinear regression using the FAST fit software package supplied with the IAsys instrument.
Circular dichroism
The CD experiments were carried out on a JASCO 710 spectropolarimeter with a 1-nm bandwidth at 0.1-nm resolution and a 1-sec response time using a 10mm path-length cell; 20–25 scans with a speed of 200 nm/min in the range of 250–190 nm were accumulated and averaged. The spectra were recorded at the peptide concentration of 10 µM in 10-mM phosphate buffer (pH 7) at 25°C. Results were expressed as mean residue molar ellipticity in deg cm /dmol.
Computational analysis
BLAST (Altschul et al. 1990) was used for sequence analyses using the Protein Data Bank (PDB; Berman et al. 2000). The MSI software INSIGHT II (Molecular Simulations, Inc.) was used on an OCTANE workstation (Silicon Graphics) for model building, analysis, and display of structural data.
The coordinates of the indolicidin were obtained from the NMR structure of indolicidin bound to dodecylphosphocholine micelles (PDB code 1G89) and those of the LPS were from the crystal structure of a complex of LPS with FhuA (PDB code 1QFG), for the molecular docking analysis. The indolicidin was docked in the lipopolysaccharide using the DOCKING module in INSIGHT II. This was followed by energy-based refinement of the model in 100 steps of steepest descent minimization, which was followed by conjugate gradient minimization until convergence. The energy minimization was carried out using the DISCOVER module. The distance-dependent dielectric constant was used during these calculations.
|
Acknowledgments |
|---|
|
References |
|---|
|
TOPAbstractIntroductionResults and DiscussionConclusionMaterials and methodsReferences |
|---|
Berman, H.M., Westbrook, J., Feng, Z., Gilliland, G., Bhat, T.N., Weissig, H., Shindyalov, I.N., and Bourne, P.E. 2000. The protein data bank. Nucleic Acid Res. 28: 235–242.
Boman, H.G. 1991. Antibacterial peptides: Key components needed in immunity. Cell 65: 205–207.[CrossRef][Medline]
Boman, H.G., Agerberth, B., and Boman, A. 1993. Mechanisms of action on Escherichia coli of cecropin P1 and PR-39, two antibacterial peptides from pig intestine. Infect. Immun. 61: 2978–2984.
Casteels, P. and Tempst, P. 1994. Apidaecin-type peptide antibiotics function through a non-poreforming mechanism involving stereospecificity. Biochem. Biophys. Res. Commun. 199: 339–345.[CrossRef][Medline]
Chen, L. and Sigler, P.B. 1999. The crystal structure of a GroEL/peptide Complex: Plasticity as a basis for substrate diversity. Cell 99: 757–768.[CrossRef][Medline]
Davies, D.R. and Cohen, G.H. 1996. Interactions of protein antigens with antibodies. Proc. Natl. Acad. Sci. 93: 7–12.
de Haas, C.J., Haas, P.J., van Kessel, K.P., and van Strijp, J.A. 1998. Affinities of different proteins and peptides for lipopolysaccharide as determined by biosensor technology. Biochem. Biophys. Res. Commun. 252: 492–496.[CrossRef][Medline]
Falla, T.J., Karunaratne, D.N., and Hancock, R.E.W. 1996. Mode of action of the antimicrobial peptide indolicidin. J. Biol. Chem. 271: 19298–19303.
Ferguson, A.D., Welte, W., Hofmann, E., Lindner, B., Holst, O., Coulton, J.W., and Diederichs, K. 2000. A conserved structural motif for lipopolysaccharide recognition by procaryotic and eucaryotic proteins. Structure 8: 585–592.[Medline]
Gallo, R.L., Ono, M., Povsic, T., Page, C., Eriksson, E., Klagsbrun, M., and Bernfield, M. 1994. Syndecans, cell surface heparan sulfate proteoglycans, are induced by a proline-rich antimicrobial peptide from wounds. Proc. Natl. Acad. Sci. 91: 11035–11039.
Gao, Y., Lecker, S., Post, M.J., Hietaranta, A.J., Li, J., Volk, R., Li, M., Sato, K., Saluja, A.K., Steer, M.L., Goldberg, A.L., and Simons, M. 2000. Inhibition of ubiquitin-proteasome pathway-mediated I 
B degradation by a naturally occurring antibacterial peptide. J. Clin. Invest. 106: 439–448.[Medline]
Gudmundsson, G.H. and Agerberth, B. 1999. Neutrophil antibacterial peptides, multifunctional effector molecules in the mammalian immune system. J. Immunol. Methods 232: 45–54.[CrossRef][Medline]
Hancock, R.E.W. 1997. Peptide antibiotics. Lancet 349: 418–422.[CrossRef][Medline]
Hancock, R.E.W., Falla, T., and Brown, M. 1995. Cationic bactericidal peptides. Adv. Microb. Physiol. 37: 135–175.[Medline]
Ido, Y., Vindigni, A., Chang, K., Stramm, L., Chance, R., Heath, W.F., DiMarchi, R.D., Di Cera, E., and Williamson, J.R. 1997. Prevention of vascular and neutral dysfunction in diabetic rats by C-peptide. Science 277: 563–566.
Keenan, R.J., Freymann, D.M., Walter, P., and Stroud, R.M. 1998. Crystal structure of the signal sequence binding subunit of the signal recognition particle. Cell 94: 181–191.[CrossRef][Medline]
Larrick, J.W., Hirata, M., Zheng, H., Zhong, J., Bolin, D., Cavaillon, J.-M., Warren, H.S., and Wright, S.C. 1994. A novel granulocyte-derived peptide with lipopolysaccharide-neutralizing activity. J. Immunol. 152: 231–240.[Abstract]
Manivel, V., Sahoo, N.C., Salunke, D.M., and Rao, K.V.S 2000. Maturation of an antibody response is governed by modulations in flexibility of the antigen-combining site. Immunity 13: 611–620.[CrossRef][Medline]
Medzhitov, R. and Janeway, Jr., C. 2000. Innate immunity. N. Engl. J. Med. 3: 338–344.
Merrifield, R.B., Juvvadi, P., Andreu, D., Ubach, J., Boman, A., and Boman, H.G. 1995. Retro and retroenantio analogs of cecropin-melittin hybrids. Proc. Natl. Acad. Sci. 92: 3449–3453.
Moore, R.A., Bates, N.C., and Hancock, R.E.W. 1986. Interaction of polycationic antibiotics with Pseudomonas aeruginosa lipopolysaccharide and lipid A studied by using dansyl-polymyxin. Antimicrob. Agents Chemother. 29: 496–500.
Nagpal, S., Gupta, V., Kaur, K.J., and Salunke, D.M. 1999. Structure-function analysis of tritrypticin, an antibacterial peptide of innate immune origin. J. Biol. Chem. 274: 23296–23304.
Pinilla, C., Appel, J.R., Campbell, G.D., Buencamino, J., Benkirane, N., Muller, S., and Greenspan, N.S. 1998. All D-peptides recognized by an anti-carbohydrate antibody identified from a positional scanning library. J. Mol. Biol. 283: 1013–1025.[CrossRef][Medline]
Rozek, A., Friedrich, C.L., and Hancock, R.E.W. 2000. Structure of the bovine antimicrobial peptide indolicidin bound to dodecylphosphocholine and sodium dodecyl sulfate micelles. Biochemistry 39:15765–15774.[CrossRef][Medline]
Schindler, P.R.G. and Teuber, M. 1975. Action of polymyxin B on bacterial membranes: Morphological changes in the cytoplasm and in the outer membrane of Salmonella typhimurium and Escherichia coli B. Antimicrob. Agents Chemother. 8: 94–104.
Selsted, M.E., Novotny, M.J., Morris, W.L., Tang, Y.-Q., Smith, W., and Cullor, J.S. 1992. Indolicidin, a novel bactericidal tridecapeptide amide from neutrophils. J. Biol. Chem. 267: 4292–4295.
Shai, Y. 1995. Molecular recognition between membrane-spanning polypeptides. Trends Biochem. Sci. 20: 460–464.[CrossRef][Medline]
Stock, D., Leslie, A.G.W., and Walker, J.E. 1999. Molecular architecture of the rotary motor in ATP synthase. Science 286: 1700–1705.
Thomas, C.J., Gangadhar, B.P., Surolia, N., and Surolia, A. 1998. Kinetics and mechanism of the recognition of endotoxin by polymyxin B. J. Am. Chem. Soc. 120: 12428–12434.[CrossRef]
Vunnam, S., Juvvadi, P., Rotondi, K.S., and Merrifield, R.B. 1998. Synthesis and study of normal, enantio, retro, and retroenantio isomers of cecropin A-melittin hybrids, their end group effects and selective enzyme inactivation. J. Peptide Res. 51: 38–44.[Medline]
Wilson, I.A. and Stanfield, R.L. 1994. Antibody–antigen interactions: New structures and new conformational changes. Curr. Opin. Struct. Biol. 4: 857–867.[CrossRef][Medline]
Woody, R.W. 1985. Circular dichroism of peptides. In The peptides: Analysis, synthesis, biology (ed. V.J. Hruby), Vol. 7, pp. 15–114. Academic Press, Inc., London.
Zanetti, M., Gennaro, R., and Romeo, D. 1995. Cathelicidins: A novel protein family with a common proregion and a variable C-terminal antimicrobial domain. FEBS Lett. 374: 1–5.[CrossRef][Medline]
Zasloff, M. 2002. Antimicrobial peptides of multicellular organisms. Nature 415: 389–395.[CrossRef][Medline]
CiteULike 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  K. J. Kaur, P. Sarkar, S. Nagpal, T. Khan, and D. M. Salunke Structure-function analyses involving palindromic analogs of tritrypticin suggest autonomy of anti-endotoxin and antibacterial activities Protein Sci., March 1, 2008; 17(3): 545 - 554. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Krishnan, S. Lomash, B. P. J. Raj, K. J. Kaur, and D. M. Salunke Paratope Plasticity in Diverse Modes Facilitates Molecular Mimicry in Antibody Response J. Immunol., June 15, 2007; 178(12): 7923 - 7931. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. M.E. Bowdish and R. E.W. Hancock Anti-endotoxin properties of cationic host defence peptides and proteins Innate Immunity, August 1, 2005; 11(4): 230 - 236. [Abstract] [PDF]
|
|
|
|
 |
|
 C.-H. Hsu, C. Chen, M.-L. Jou, A. Y.-L. Lee, Y.-C. Lin, Y.-P. Yu, W.-T. Huang, and S.-H. Wu Structural and DNA-binding studies on the bovine antimicrobial peptide, indolicidin: evidence for multiple conformations involved in binding to membranes and DNA Nucleic Acids Res., July 20, 2005; 33(13): 4053 - 4064. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. Japelj, P. Pristovsek, A. Majerle, and R. Jerala Structural Origin of Endotoxin Neutralization and Antimicrobial Activity of a Lactoferrin-based Peptide J. Biol. Chem., April 29, 2005; 280(17): 16955 - 16961. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
