1yeb
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(New page: 200px<br /><applet load="1yeb" size="450" color="white" frame="true" align="right" spinBox="true" caption="1yeb, resolution 1.95Å" /> '''STRUCTURE DETERMINAT...)
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Revision as of 04:35, 21 November 2007
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STRUCTURE DETERMINATION AND ANALYSIS OF YEAST ISO-2-CYTOCHROME C AND A COMPOSITE MUTANT PROTEIN
Overview
As part of a study of protein folding and stability, the three-dimensional, structures of yeast iso-2-cytochrome c and a composite protein (B-2036), composed of primary sequences of both iso-1 and iso-2-cytochromes c have, been solved to 1.9 A and 1.95 A resolutions, respectively, using X-ray, diffraction techniques. The sequences of iso-1 and iso-2-cytochrome c, share approximately 84% identity and the B-2036 composite protein has, residues 15 to 63 from iso-2-cytochrome c with the rest being derived form, the iso-1 protein. Comparison of these structures reveals that amino acid, substitutions result in alterations in the details of intramolecular, interactions. Specifically, the substitution Leu98Met results in the, filling of an internal cavity present in iso-1-cytochrome c. Further, substitutions of Val20Ile and Cys102Ala alter the packing of secondary, structure elements in the iso-2 protein. Blending the isozymic amino acid, sequences in this latter area results in the expansion of the volume of an, internal cavity in the B-2036 structure to relieve a steric clash between, Ile20 and Cys102. Modification of hydrogen bonding and protein packing, without disrupting the protein fold is illustrated by the His26Asn and, Asn63Ser substitutions between iso-1 and iso-2-cytochromes c., Alternatively, a change in main-chain fold is observed at Gly37 apparently, due to a remote amino acid substitution. Further structural changes occur, at Phe82 and the amino terminus where a four residue extension is present, in yeast iso-2-cytochrome c. An additional comparison with all other, eukaryotic cytochrome c structures determined to date is presented, along, with an analysis of conserved water molecules. Also determined are the, midpoint reduction potentials of iso-2 and B-2036 cytochromes c using, direct electrochemistry. The values obtained are 286 and 288 mV, respectively, indicating that the amino acid substitutions present have, had only a small impact on the heme reduction potential in comparison to, iso-1-cytochrome c, which has a reduction potential of 290 mV.
About this Structure
1YEB is a Single protein structure of sequence from Saccharomyces cerevisiae with SO4, TML and HEM as ligands. Full crystallographic information is available from OCA.
Reference
Structure determination and analysis of yeast iso-2-cytochrome c and a composite mutant protein., Murphy ME, Nall BT, Brayer GD, J Mol Biol. 1992 Sep 5;227(1):160-76. PMID:1326054
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