1h9k: Difference between revisions

The X-ray structures of the cytoplasmic molybdate-binding protein ModG, from Azotobacter vinelandii in two different crystal forms have been, determined. For such a small protein it is remarkably complex. Each 14.3, kDa subunit contains two small beta-barrel domains, which display an, OB-fold motif, also seen in the related structure of ModE, a, molybdenum-dependent transcriptional regulator, and very recently in the, Mop protein that, like ModG, has been implicated in molybdenum homeostasis, within the cell. In contrast to earlier speculation, the functional unit, of ModG is actually not a dimer (as in ModE), but a trimer capable of, binding a total of eight molybdate molecules that are distributed between, two disparate types of site. All the binding sites are located at subunit, interfaces, with one type lying on a crystallographic 3-fold axis, whilst, the other lies between pairs of subunits. The two types of site are linked, by short hydrogen bond networks that may suggest a cooperative binding, mechanism. A superposition of two subunits of the ModG trimer on the, apo-ModE dimer allows the probable locations of the molybdate-binding, sites of the latter to be assigned. Through structural comparisons with, other oxyanion-binding proteins, including Mop and ModE, it is possible to, speculate about ligand-binding affinities, selectivity and evolution., Copyright 12001 Academic Press.

1H9K is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Azotobacter_vinelandii Azotobacter vinelandii] with WO4 and PO4 as [http://en.wikipedia.org/wiki/ligands ligands]. Structure known Active Sites: WO1 and WO2. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1H9K OCA].  

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