1jfu
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(New page: 200px<br /><applet load="1jfu" size="450" color="white" frame="true" align="right" spinBox="true" caption="1jfu, resolution 1.6Å" /> '''CRYSTAL STRUCTURE OF ...)
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Revision as of 16:05, 20 November 2007
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CRYSTAL STRUCTURE OF THE SOLUBLE DOMAIN OF TLPA FROM BRADYRHIZOBIUM JAPONICUM
Overview
TlpA is an unusual thioredoxin-like protein present in the nitrogen-fixing, soil bacterium Bradyrhizobium japonicum. A hydrophobic N-terminal, transmembrane domain anchors it to the cytoplasmic membrane, whereby the, hydrophilic thioredoxin domain becomes exposed to the periplasmic space., There, TlpA catalyses an essential reaction, probably a reduction, in the, biogenesis of cytochrome aa(3). The soluble thioredoxin domain, (TlpA(sol)), devoid of the membrane anchor, was purified and crystallized., Oxidized TlpA(sol) crystallized as a non-covalent dimer in the space group, P2(1)2(1)2(1). The X-ray structure analysis was carried out by isomorphous, replacement using a xenon derivative. This resulted in a high-resolution, (1.6 A) three-dimensional structure that displayed all of the features of, a classical thioredoxin fold. A number of peculiar structural details were, uncovered: (i) Only one of the two active-site-cysteine sulphurs (Cys72, the one closer to the N terminus) is exposed on the surface, making it the, likely nucleophile for the reduction of target proteins. (ii) TlpA(sol), possesses a unique structural disulphide bond, formed between Cys10 and, Cys155, which connects an unprecedented N-terminal alpha helix with a beta, sheet near the C terminus. (iii) An insertion of about 25 amino acid, residues, not found in the thioredoxin prototype of Escherichia coli, contributes only marginally to the thioredoxin fold, but forms an extra, surface-exposed alpha helix. This region plus another surface-exposed, stretch (-Ile-Gly-Arg-Ala-), which is absent even in the closest TlpA, relatives, might be considered as specificity determinants for the, recognition of target proteins in the periplasm. The TlpA(sol) structure, paves the way towards unraveling important structure-function, relationships by rational mutagenesis.
About this Structure
1JFU is a Single protein structure of sequence from Bradyrhizobium japonicum. Full crystallographic information is available from OCA.
Reference
Structure of the soluble domain of a membrane-anchored thioredoxin-like protein from Bradyrhizobium japonicum reveals unusual properties., Capitani G, Rossmann R, Sargent DF, Grutter MG, Richmond TJ, Hennecke H, J Mol Biol. 2001 Aug 31;311(5):1037-48. PMID:11531338
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