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Journal Issue - Volume 5 Issue 3 (March 1996)

Abstract The Src homologous and collagen‐like (SHC) protein plays an essential role in signal transduction pathways in that it participates in the chain of events that leads to the activation of the protein Ras. The crystal structure of the SH2 domain of SHC has been determined using the method of multiple isomorphous replacement at a resolution of 2.5 Å. The SH2 domain of SHC is similar in fold to other SH2 domains. The...

Abstract X‐ray diffraction analysis at 1.5 A resolution has confirmed the helical conformation of a de novo designed 18‐residue peptide. However, the crystal structure reveals the formation of continuous molecular layers of parallel‐packed amphiphilic helices as a result of much more extensive helix‐helix interactions than predicted. The crystal packing arrangement, by virtue of distinct antiparallel packing interactions, segregates...

Abstract A new class of divalent thrombin inhibitors is described that contains an α‐keto‐amide transition‐state mimetic linking an active site binding group and a group that binds to the fibrinogen‐binding exosite. The X‐ray crystallographic structure of the most potent member of this new class, CVS995, shows many features in common with other divalent thrombin inhibitors and clearly defines the transition‐state‐like binding of the...

Abstract In vertebrates, there are different adenylate kinases in the compartments cytosol, mitochondrial intermembrane space, and mitochondrial matrix. Here, we report the spatial structure of the intermembrane species established in two crystal forms by X‐ray diffraction analyses at 1.92 and 2.1 Å resolution. In both structures, the enzyme is unligated, and thus in an “open” conformation. The enzyme was prepared from bovine liver,...

Abstract The structure of the phosphorylated form of the histidine‐containing phosphocarrier protein HPr from Escherichia coli has been solved by NMR and compared with that of unphosphorylated HPr. The structural changes that occur upon phosphorylation of His 15, monitored by changes in NOE patterns, 3JNHHα‐coupling constants, and chemical shifts, are limited to the region around the phosphorylation site. The His 15 backbone torsion angles...

Abstract An understanding of the structure‐function relationship of nerve growth factor (NGF) requires precise knowledge of all the residues and regions that participate in NGF receptor binding, receptor activation, and biological activity. Seven recombinant human NGF mutants having alanine substituted for residues located either in the NGF dimer interface or β‐strand region were studied to determine the role of each amino acid...

Abstract Bacteriorhodopsin (bR) is a light‐driven proton pump from Halobacterium salinarium and is a model system for studying membrane protein folding, stability, function, and structure. bR is composed of bacterio‐opsin (bO), the 248‐amino acid apo protein, and all‐trans retinal, which is linked to lysine 216 via a protonated Schiff base. A bO gene (sbOd) possessing 29 unique restriction sites and a carboxyl‐terminal purification epitope...

Abstract We have generated mutants of Drosophila calmodulin in which pairs of calcium‐binding sites are mutated so as to prevent calcium binding. In all sites, the mutation involves replacement of the —Z position glutamate residue with glutamine. Mutants inactivated in both N‐terminal sites (B12Q) or both C‐terminal sites (B34Q), and two mutants with one N‐ and one C‐terminal site inactivated (B13Q and B24Q) were generated. The...

Abstract We have studied the effect of the components of the GroE molecular chaperone machine on the refolding of the Escherichia coli enzyme β‐galactosidase, a tetrameric protein whose 116‐kDa protomers should not completely fit within the central cavity of the GroEL toroid. In the absence of other additives, GroEL formed a weak complex with chemically denatured β‐galactosidase, reduced its propensity to aggregate, and increased the recovery...

Abstract Electrospray ionization mass spectrometry was used to investigate the structure of the Escherichia coli chaperone protein SecB. It was determined that the N‐terminal methionine of SecB has been removed and that more than half of all SecB monomers are additionally modified, most likely by acetylation of the N‐terminus or a lysine. The use of gentle mass spectrometer interface conditions showed that the predominant, oligomeric form of...

Abstract The three‐dimensional solution structure of the HIV‐1 protease homodimer, MW 22.2 kDa, complexed to a potent, cyclic urea‐based inhibitor, DMP323, is reported. This is the first solution structure of an HIV protease/inhibitor complex that has been elucidated. Multidimensional heteronuclear NMR spectra were used to assemble more than 4,200 distance and angle constraints. Using the constraints, together with a hybrid distance...

Abstract The failure to appreciate that the hydration of polar groups is a major contribution to the entropy of protein unfolding has led to considerable underestimates for the loss of configurational freedom when a protein chain folds.

Abstract The thermal unfolding process of a chimeric 3‐isopropylmalate dehydrogenase made of parts from an extreme thermophile, Thermus thermophilus, and a mesophile, Bacillus subtilis, enzymes was studied by CD spectrophotometry and differential scanning calorimetry (DSC). The enzyme is a homodimer with a subunit containing two structural domains. The DSC melting profile of the chimeric enzyme in 20 mM NaHCO3, pH 10.4, showed two endothermic peaks,...

Abstract The kinetics of renaturation of bovine carbonic anhydrase II (CAII) were studied from 4° to 36°, at the relatively high [CAII] of 4 mg/mL. Following dilution to 1 M guanidinium chloride, aggregate formation is very rapid and reduces the formation of active enzyme. The CAII activity yield at 150 min, 20° (∼60%), is greater than that at either 4° or 36°. However, if refolding is conducted at 4°, aggregation is reduced...

Abstract A mollusk‐specific toxin, TxVIIA, having potent paralytic activity was isolated from the venom of sea snail Conus textile (Fainzilber M et al., 1991, Eur J Biochem 202:589–595). The structure reported above was based upon amino acid analysis and the Edman degradation. We have recently reinvestigated this toxin employing some of the most novel techniques in mass spectrometry. We now report a revised structure based primarily on...

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