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Journal Issue - Volume 4 Issue 8 (August 1995)

Abstract The 3C proteinases are a novel group of cysteine proteinases with a serine proteinase‐like fold that are responsible for the bulk of polyprotein processing in the Picornaviridae. Because members of this viral family are to blame for several ongoing global pandemic problems (rhinovirus, hepatitis A virus) as well as sporadic outbreaks of more serious pathologies (poliovirus), there has been continuing interest over the last...

Abstract We present a structural analysis of a peptide, the sequence of which includes amino acids that show preferences for specific positions near the N‐ and C‐termini in protein helices. This peptide has the sequence ac‐YMSEDELKAAEAAFKRHGVP‐amide, which includes a strong version of an N‐terminal Harper‐Rose capping box structure as well as a Gly located close to the C‐terminus designed to elucidate its role in C‐terminal capping....

Abstract Limited information is available on inherent stabilities of four‐chain coiled‐coils. We have developed a model system to study this folding motif using synthetic peptides derived from sequences contained in the tetramerization domain of Lac repressor. These peptides are tetrameric as judged by both gel filtration and sedimentation equilibrium and the tetramers are fully helical as determined by CD. The four‐chain...

Abstract Residues P19, L28, C31, and C32 have been implicated (Di Donato A, Cafaro V, D'Alessio G, 1994, J Biol Chem 269:17394–17396; Mazzarella L, Vitagliano L, Zagari A, 1995, Proc Natl Acad Sci USA: forthcoming) with key roles in determining the dimeric structure and the N‐terminal domain swapping of seminal RNase. In an attempt to have a clearer understanding of the structural and functional significance of these residues in seminal RNase, ...

Abstract The structure of the potassium channel blocker agitoxin 2 was solved by solution NMR methods. The structure consists of a triple‐stranded antiparallel β‐sheet and a single helix covering one face of the β‐sheet. The cysteine side chains connecting the β‐sheet and the helix form the core of the molecule. One edge of the β‐sheet and the adjacent face of the helix form the interface with the Shaker K+ channel. The fold of agitoxin is...

Abstract Synthetic peptides patterned after the predicted transmembrane sequence of botulinum toxin A were used as tools to identify an ion channel‐forming motif. A peptide denoted BoTxATM, with the sequence GAVILLEFIPEIAI PVLGTFALV, forms cation‐selective channels when reconstituted in planar lipid bilayers. As predicted, the self‐assembled conductive oligomers express heterogeneous single‐channel conductances. The most frequent...

Abstract The X‐ray structure of a mutant version of Escherichia coli alkaline phosphatase (H412N) in which His‐412 was replaced by Asn has been determined at both low (‐Zn) and high (+Zn) concentrations of zinc. In the wild‐type structure, His‐412 is a direct ligand to one of the two catalytically critical zinc atoms (Zn,) in the active site. Characterization of the H412N enzyme in solution revealed that the mutant enzyme required high...

Abstract The activity of Tsp, a periplasmic endoprotease of Escherichia coli, has been characterized by assaying the cleavage of protein and peptide substrates, determining the cleavage sites in several substrates, and investigating the kinetics of the cleavage reaction. Tsp efficiently cleaves substrates that have apolar residues and a free α‐carboxylate at the C‐terminus. Tsp cleaves its substrates at a discrete number of sites but with...

Abstract Protein‐solvent interactions were analyzed using an optimization parameter based on the ratio of the solvent‐accessible area in the native and the unfolded protein structure. The calculations were performed for a set of 183 nonhomologous proteins with known three‐dimensional structure available in the Protein Data Bank. The dependence of the total solvent‐accessible surface area on the protein molecular mass was analyzed....

Abstract The energetics of barstar denaturation have been studied by CD and scanning microcalorimetry in an extended range of pH and salt concentration. It was shown that, upon increasing temperature, barstar undergoes a transition to the denatured state that is well approximated by a two‐state transition in solutions of high ionic strength. This transition is accompanied by significant heat absorption and an increase in heat...

Abstract The denaturation and renaturation of carbonic anhydrase II (CAII) has been studied in several laboratories. Both thermodynamic and kinetic evidence support the existence of at least two intermediates between denatured and native protein. Previous studies have shown that on rapid dilution of a CAII solution from 5 M to 1 M guanidinium chloride, aggregation strongly competes with renaturation at higher protein concentrations,...

Abstract Urea‐induced dissociation and unfolding of manganese · glutamine synthetase (Mn‐GS) have been studied at 37 °C (pH 7) by spectroscopic and calorimetric methods. In 0 to ∼2 M urea, Mn‐GS retains its dodecameric structure and full catalytic activity. Mn‐GS is dissociated into subunits in 6 M urea, as evidenced by a 12‐fold decrease in 90° light scattering and a monomer molecular weight of 51,800 in sedimentation equilibrium...

Abstract Interaction with 8‐anilino‐1‐naphthalenesulfonate (ANS) is widely used to detect molten globule states of proteins. We have found that even with stable partially folded states, the development of the fluorescence enhancements resulting from such interactions can be relatively slow and kinetically complex. This is probably because initial binding of the dye can induce subsequent changes in the protein structure, so that the...

Abstract The development of “soft” ionization methods has enabled the mass spectrometric analysis of higher‐order structural features of proteins. We have applied electrospray ionization mass spectrometry (ESI‐MS) to the analysis of the number and composition of polypeptide chains in homomeric and heteromeric leucine zippers. In comparison with other methods that have been used to analyze leucine zippers, such as analytical...

Abstract Far‐UV CD, 1H‐NMR, and Fourier transform infrared (FTIR) spectroscopy are three of the most commonly used methods for the determination of protein secondary structure composition. These methods are compared and evaluated as a means of establishing isostructural metal substitution in metalloproteins, using the crystallographically defined rubredoxin from Desulfovibrio gigas and its well‐characterized cadmium derivative as a model...

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