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Journal Issue - Volume 16 Issue 9 (September 2007)

Abstract It is becoming increasingly apparent that heat shock proteins play an important role in the survival of Plasmodium falciparum against temperature changes associated with its passage from the cold‐blooded mosquito vector to the warm‐blooded human host. Interest in understanding the possible role of P. falciparum Hsp70s in the life cycle of the parasite has led to the identification of six HSP70 genes. Although most research attention has focused...

Abstract As membrane transporter proteins, VGLUT1–3 mediate the uptake of glutamate into synaptic vesicles at presynaptic nerve terminals of excitatory neural cells. This function is crucial for exocytosis and the role of glutamate as the major excitatory neurotransmitter in the central nervous system. The three transporters, sharing 76% amino acid sequence identity in humans, are highly homologous but differ in regional expression...

Abstract Sm‐like proteins are ubiquitous ring‐shaped oligomers that exhibit a variety of nucleic acid‐binding activities. They have been linked functionally to various cellular events involving RNA, and it is generally believed that their activity is exerted via the passive binding of nucleic acids. Our earlier studies of the Sm‐like Escherichia coli protein Hfq provided the first evidence indicating that Hfq is an ATP‐binding protein. Using a...

Abstract The native form of serpins (serine protease inhibitors) is a metastable conformation, which converts into a more stable form upon complex formation with a target protease. It has been suggested that movement of helix‐F (hF) and the following loop connecting to strand 3 of β‐sheet A (thFs3A) is critical for such conformational change. Despite many speculations inferred from analysis of the serpin structure itself, direct...

Abstract Quantum mechanical optimizations of theoretical enzymes (theozymes), which are predicted catalytic arrays of biological functionalities stabilizing a transition state, have been carried out for a set of nine diverse enzyme active sites. For each enzyme, the theozyme for the rate‐determining transition state plus the catalytic groups modeled by side‐chain mimics was optimized using B3LYP/6–31G(d) or, in one case, HF/3–21G(d)...

Abstract The second osmotic virial coefficients of seven proteins—ovalbumin, ribonuclease A, bovine serum albumin, α‐lactalbumin, myoglobin, cytochrome c, and catalase—were measured in salt solutions. Comparison of the interaction trends in terms of the dimensionless second virial coefficient b2 shows that, at low salt concentrations, protein–protein interactions can be either attractive or repulsive, possibly due to the anisotropy...

Abstract Among the transcription factors, the helix‐turn‐helix (HTH) GntR family comprised of FadR, HutC, MocR, YtrA, AraR, and PlmA subfamilies regulates the most varied biological processes. Generally, proteins belonging to this family contain an N‐terminal DNA‐binding domain and a C‐terminal effector‐binding/oligomerization domain. The members of the YtrA subfamily are much shorter than other members of this family, with chain...

Abstract We investigate the mechanisms used by proteins to maintain thermostability throughout a wide range of temperatures. We use the quasi‐chemical approximation to estimate interaction strengths for psychrophiles, mesophiles, thermophiles, and hyperthermophiles. Our results highlight the importance of core packing in thermophilic stability. Although we observed an increase in the number of charged residues, the contribution of...

Abstract Mycobacterium leprae protein ML2640c belongs to a large family of conserved hypothetical proteins predominantly found in mycobacteria, some of them predicted as putative S‐adenosylmethionine (AdoMet)‐dependent methyltransferases (MTase). As part of a Structural Genomics initiative on conserved hypothetical proteins in pathogenic mycobacteria, we have determined the structure of ML2640c in two distinct crystal forms. As...

Abstract The tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors of the matrix metalloproteinases (MMPs). Since unregulated MMP activities are linked to arthritis, cancer, and atherosclerosis, TIMP variants that are selective inhibitors of disease‐related MMPs have potential therapeutic value. The structures of TIMP/MMP complexes reveal that most interactions with the MMP involve the N‐terminal pentapeptide of...

Abstract Relative to other parvalbumin isoforms, the mammalian β‐parvalbumin (oncomodulin) displays attenuated divalent ion affinity. High‐resolution structural data for the Ca2+‐bound protein have provided little insight into the physical basis for this behavior, prompting an examination of the unliganded state. This article describes the solution structure and peptide backbone dynamics of Ca2+‐free rat β‐parvalbumin (β‐PV). Ca2+ removal...

Abstract The partial molar volume (PMV) change associated with the pressure‐induced structural transition of ubiquitin is analyzed by the three‐dimensional reference interaction site model (3D‐RISM) theory of molecular solvation. The theory predicts that the PMV decreases upon the structural transition, which is consistent with the experimental observation. The volume decomposition analysis demonstrates that the PMV reduction is...

Abstract The cysteine‐rich somatomedin B domain (SMB) of the matrix protein vitronectin is involved in several important biological processes. First, it stabilizes the active conformation of the plasminogen activator inhibitor (PAI‐1); second, it provides the recognition motif for cell adhesion via the cognate integrins (αvβ3, αvβ5, and αIIbβ3); and third, it binds the complex between urokinase‐type plasminogen activator (uPA) and its...

Abstract Previous results indicate that the folding pathways of cytochrome c and other proteins progressively build the target native protein in a predetermined stepwise manner by the sequential formation and association of native‐like foldon units. The present work used native state hydrogen exchange methods to investigate a structural anomaly in cytochrome c results that suggested the concerted folding of two segments that have little...

Abstract In the presence of moderate (2–4 M) urea concentrations the tetrameric enzyme, glycine N‐methyltransferase (GNMT), dissociates into compact monomers. Higher concentrations of urea (7–8 M) promote complete denaturation of the enzyme. We report here that the H176N mutation in this enzyme, found in humans with hypermethioninaemia, significantly decreases stability of the tetramer, although H176 is located far from the...

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