5pal
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(New page: 200px<br /><applet load="5pal" size="450" color="white" frame="true" align="right" spinBox="true" caption="5pal, resolution 1.54Å" /> '''CRYSTAL STRUCTURE OF...)
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Revision as of 17:32, 20 November 2007
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CRYSTAL STRUCTURE OF THE UNIQUE PARVALBUMIN COMPONENT FROM MUSCLE OF THE LEOPARD SHARK (TRIAKIS SEMIFASCIATA). THE FIRST X-RAY STUDY OF AN ALPHA-PARVALBUMIN
Overview
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 molecular replacement method using pike, 4.10 parvalbumin as a model. The final structure refinement resulted in an, R-factor of 17.3% for 11,363 independent reflections at 1.54 A resolution., The shark parvalbumin shows the main features of all parvalbumins: the, folding of the chain including six alpha-helices, the salt bridge between, Arg75 and Glu81, and the hydrophobic core. Compared to the structure of, beta-parvalbumins from pike and carp, one main difference is observed: the, chain is one residue longer and this additional residue, which extends the, F helix, is involved through its C-terminal carboxylate group in a network, of electrostatic contacts with two basic residues, His31 in the B helix, and Lys36 in the BC segment. Furthermore, hydrogen bonds exist between the, side-chains of Gln108 (F helix) and Tyr26 (B helix). There is therefore a, "locking" of the tertiary structure through contacts between two, sequentially distant regions in the protein and this is likely to, contribute to making the stability of an alpha-parvalbumin higher in, comparison to that of a beta-parvalbumin. The lengthening of the, C-terminal F helix by one residue appears to be a major feature of, alpha-parvalbumins in general, owing to the homologies of the amino acid, sequences. Besides the lengthening of the C-terminal helix, the, classification of the leopard shark parvalbumin in the alpha-series rests, upon the observation of Lys13, Leu32, Glu61 and Val66. As this is the, first crystal structure description of a parvalbumin from the, alpha-phylogenetic lineage, it was hoped that it would clearly determine, the presence or absence of a third cation binding site in parvalbumins, belonging to the alpha-lineage. In beta-pike pI 4.10 parvalbumin, Asp61, participates as a direct ligand of a third site, the satellite of the CD, site. In shark parvalbumin, as in nearly all alpha-parvalbumins, one finds, Glu at position 61. Unfortunately, the conformation of the polar head of, Glu61 cannot be inferred from the X-ray data.(ABSTRACT TRUNCATED AT 400, WORDS)
About this Structure
5PAL is a Single protein structure of sequence from Triakis semifasciata with CA as ligand. Full crystallographic information is available from OCA.
Reference
Crystal structure of the unique parvalbumin component from muscle of the leopard shark (Triakis semifasciata). The first X-ray study of an alpha-parvalbumin., Roquet F, Declercq JP, Tinant B, Rambaud J, Parello J, J Mol Biol. 1992 Feb 5;223(3):705-20. PMID:1542115
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