The three-dimensional structure of parvalbumin from leopard shark (Triakis semifasciata) with 109 amino acid residues (alpha-series) is described at 1.54 A resolution. Crystals were grown at 20 degrees C from 2.9 M-potassium/sodium phosphate solutions at pH 5.6. The space group is P3(1)21 and unit cell dimensions are a = b = 32.12 A and c = 149.0 A. The structure has been solved by the molecula...

Two-dimensional NMR spectroscopy has been used to obtain sequence-specific 1H NMR assignments for the IgG-binding B2-domain of streptococcal protein G. Secondary structure elements were identified from analysis of characteristic backbone-backbone NOE patterns and amide proton exchange data. The B2-domain contains a four-stranded beta-sheet region in which the two inner strands form a parallel b...

The three-dimensional crystal structure of the bacterial chemotaxis protein CheY with the essential Mg2+ cation bound to the active site reveals large conformational changes caused by the metal binding. Displacements of up to 10 A are observed in several residues at the N terminus of alpha-helix 4 and in the preceding loop. One turn of this helix unwinds, and an Asn residue that was located ins...

Amino acid sequences homologous to 259KLVGKL (X)16KLLR284 of human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) are conserved in several nucleotide polymerizing enzymes. This amino acid motif has been identified in the crystal structure model as an element of the enzyme's nucleic acid binding apparatus. It is part of the helix-turn-helix structure, alpha H-turn-alpha I, within...

We have solved the crystal structure of a segment of nonerythroid alpha-spectrin (alphaII) consisting of the first 147 residues to a resolution of 2.3 A. We find that the structure of this segment is generally similar to a corresponding segment from erythroid alpha-spectrin (alphaI) but exhibits unique differences with functional significance. Specific features include the following: (i) an irr...

Helix content of peptides with various uncharged nonaromatic amino acids at either the N-terminal or C-terminal position has been determined. The choice of N-terminal amino acid has a major effect on helix stability: asparagine is the best, glycine is very good, and glutamine is the worst helix-stabilizing amino acid at this position. The rank order of helix stabilization parallels the frequenc...