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Journal Issue - Volume 5 Issue 12 (December 1996)

Abstract The C2 domain is a Ca2+‐binding motif of approximately 130 residues in length originally identified in the Ca2+‐dependent isoforms of protein kinase C. Single and multiple copies of C2 domains have been identified in a growing number of eukaryotic signalling proteins that interact with cellular membranes and mediate a broad array of critical intracellular processes, including membrane trafficking, the generation of lipid‐second...

Abstract The three‐dimensional solution‐ and solid‐state structures of the human immunodeficiency virus type‐1 (HIV‐1) matrix protein have been determined recently in our laboratories by NMR and X‐ray crystallographic methods (Massiah et al. 1994. J Mol Biol 244:198–223; Hill et al. 1996. Proc Natl Acad Sci USA 93:3099–3104). The matrix protein exists as a monomer in solution at low millimolar protein concentrations, but forms trimers in three...

Abstract To further investigate the ways in which proteins respond to changes in the length of the polypeptide chain, a series of 32 insertions and five deletions were made within nine different α‐helices of T4 lysozyme. In most cases, the inserted amino acid was a single alanine, although in some instances up to four residues, not necessarily alanine, were used. Different insertions destabilized the protein by different amounts,...

Abstract It has been established that phosphate analogues can activate glycogen phosphorylase reconstituted with pyridoxal in place of the natural cofactor pyridoxal 5′‐phosphate (Chang YC, McCalmont T, Graves DJ. 1983. Biochemistry 22:4987–4993). Pyridoxal phosphorylase b has been studied by kinetic, ultracentrifugation, and X‐ray crystallographic experiments. In solution, the catalytically active species of pyridoxal phosphorylase b adopts a...

Abstract We have determined the crystal structure of dUTP pyrophosphatase (dUTPase) from feline immunodeficiency virus (FIV) at 1.9 Å resolution. The structure has been solved by the multiple isomorphous replacement (MIR) method using a P63 crystal form. The results show that the enzyme is a trimer of 14.3 kDa subunits with marked structural similarity to E. coli dUTPase. In both enzymes the C‐terminal strand of an anti‐parallel β‐barrel participates in...

Abstract The crystal structure of a complex formed by the interaction between proteinase K and a designed octapeptide amide, N‐Ac‐Pro‐Ala‐Pro‐Phe‐DAla‐Ala‐Ala‐Ala‐NH2, has been determined at 2.5 Å resolution and refined to an R‐factor of 16.7% for 7,430 reflections in the resolution range of 8.0–2.50 Å. The inhibitor forms a stable complex through a series of hydrogen bonds and hydrophobic interactions with the protein atoms and water molecules. The...

Abstract The three‐dimensional structure of bacterial sphingomyelinase (SMase) was predicted using a protein fold recognition method; the search of a library of known structures showed that the SMase sequence is highly compatible with the mammalian DNase I structure, which suggested that SMase adopts a structure similar to that of DNase I. The amino acid sequence alignment based on the prediction revealed that, despite the lack of...

Abstract The interleukin‐2 receptor (IL‐2R) is composed of at least three cell surface subunits, IL‐2Rα, IL‐2Rβ, and IL‐2Rγc. On activated T‐cells, the α‐ and β‐subunits exist as a preformed heterodimer that simultaneously captures the IL‐2 ligand as the initial event in formation of the signaling complex. We used BIAcore to compare the binding of IL‐2 to biosensor surfaces containing either the α‐subunit, the β‐subunit, or both subunits...

Abstract The CD spectra of human carbonic anhydrase I and II and bovine carbonic anhydrase III were recorded and analyzed. The 3D structures of these isoenzymes are known, showing very similar secondary structure and polypeptide‐chain fold. The tryptophan content, however, differs between the isoenzymes, i.e., isoenzymes I, II, and III possess 6, 7, and 8 tryptophans, respectively. All of the tryptophans except the additional...

Abstract There are four groups of RNA bacteriophages with distinct antigenic and physicochemical properties due to differences in surface residues of the viral coat proteins. Coat proteins also play a role as translational repressor during the viral life cycle, binding an RNA hairpin within the genome. In this study, the first crystal structure of the coat protein from a Group II phage GA is reported and compared to the Group I MS2...

Abstract Cytochrome c‐550 of Thiobacillus versutus functions as an electron transfer protein in a chain of redox proteins that enables T. versutus to grow on methylamine. It is a single‐heme protein of 134 residues, related to mitochondrial cytochrome c. Cytochrome c‐550, as well as several other bacterial c2‐type cytochromes, contain a C‐terminal extension of 13–16 amino acids of unknown function, compared to mitochondrial cytochrome c. ...

Abstract An unresolved key issue in the mechanism of protein folding assisted by the molecular chaperone GroEL is the nature of the substrate protein bound to the chaperonin at different stages of its reaction cycle. Here we describe the conformational properties of human dihydrofolate reductase (DHFR) bound to GroEL at different stages of its ATP‐driven folding reaction, determined by hydrogen exchange labeling and electrospray...

Abstract Complete dissociation of dimeric plasma sex steroid‐binding protein (SBP or SHBG) was obtained in 6 M urea at 10 °C. Removal of urea resulted in the refolding of monomers, followed by reformation of dimeric SBP, which migrates with the same mobility as the native protein. Dimerization does not require Ca++ or steroid. Renatured monomers yield dimers with dissociation constants for 5α‐dihydrotesterone (DHT) and 17β‐estradiol (E2)...

Abstract The rate‐limiting step for the absorption of insulin solutions after subcutaneous injection is considered to be the dissociation of self‐associated hexamers to monomers. To accelerate this absorption process, insulin analogues have been designed that possess full biological activity and yet have greatly diminished tendencies to self‐associate. Sedimentation velocity and static light scattering results show that the presence...

Abstract Lanthanide luminescence was used to examine the effects of posttranslational adenylylation on the metal binding sites of Escherichia coli glutamine synthetase (GS). These studies revealed the presence of two lanthanide ion binding sites of GS of either adenylylation extrema. Individual emission decay lifetimes were obtained in both H20 and D2O solvent systems, allowing for the determination of the number of water molecules coordinated to each...

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