2j89: Difference between revisions

The genome of Populus trichocarpa contains five methionine sulfoxide, reductase A genes. Here, both cytosolic (cMsrA) and plastidial (pMsrA), poplar MsrAs were analyzed. The two recombinant enzymes are active in the, reduction of methionine sulfoxide with either dithiothreitol or poplar, thioredoxin as a reductant. In both enzymes, five cysteines, at positions, 46, 81, 100, 196, and 202, are conserved. Biochemical and enzymatic, analyses of the cysteine-mutated MsrAs support a catalytic mechanism, involving three cysteines at positions 46, 196, and 202. Cys(46) is the, catalytic cysteine, and the two C-terminal cysteines, Cys(196) and, Cys(202), are implicated in the thioredoxin-dependent recycling mechanism., Inspection of the pMsrA x-ray three-dimensional structure, which has been, determined in this study, strongly suggests that contrary to bacterial and, Bos taurus MsrAs, which also contain three essential Cys, the last, C-terminal Cys(202), but not Cys(196), is the first recycling cysteine, that forms a disulfide bond with the catalytic Cys(46). Then Cys(202), forms a disulfide bond with the second recycling cysteine Cys(196) that is, preferentially reduced by thioredoxin. In agreement with this assumption, Cys(202) is located closer to Cys(46) compared with Cys(196) and is, included in a (202)CYG(204) signature specific for most plant MsrAs. The, tyrosine residue corresponds to the one described to be involved in, substrate binding in bacterial and B. taurus MsrAs. In these MsrAs, the, tyrosine residue belongs to a similar signature as found in plant MsrAs, but with the first C-terminal cysteine instead of the last C-terminal, cysteine.

2J89 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Populus_trichocarpa Populus trichocarpa] with BME as [http://en.wikipedia.org/wiki/ligand ligand]. Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=2J89 OCA].  

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