1o57: Difference between revisions

[[Image:1o57.gif|left|200px]]<br /><applet load="1o57" size="350" color="white" frame="true" align="right" spinBox="true"  

The purine repressor from Bacillus subtilis, PurR, represses transcription from a number of genes with functions in the synthesis, transport, and metabolism of purines. The 2.2-A crystal structure of PurR reveals a two-domain protein organized as a dimer. The larger C-terminal domain belongs to the PRT structural family, in accord with a sequence motif for binding the inducer phosphoribosylpyrophosphate (PRPP). The PRT domain is fused to a smaller N-terminal domain that belongs to the winged-helix family of DNA binding proteins. A positively charged surface on the winged-helix domain likely binds specific DNA sequences in the recognition site. A second positively charged surface surrounds the PRPP site at the opposite end of the PurR dimer. Conserved amino acids in the sequences of PurR homologs in 21 gram-positive bacteria cluster on the proposed recognition surface of the winged-helix domain and around the PRPP binding site at the opposite end of the molecule, supporting a common function of DNA and PRPP binding for all of the proteins. The structure supports a binding mechanism in which extended regions of DNA interact with extensive protein surface. Unlike most PRT proteins, which are phosphoribosyltransferases (PRTases), PurR lacks catalytic activity. This is explained by a tyrosine side chain that blocks the site for a nucleophile cosubstrate in PRTases. Thus, B. subtilis has adapted an enzyme fold to serve as an effector-binding domain and has used it in a novel combination with the DNA-binding winged-helix domain as a repressor of purine genes.

1O57 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacillus_subtilis Bacillus subtilis] with <scene name='pdbligand=SO4:'>SO4</scene>, <scene name='pdbligand=EPE:'>EPE</scene>, <scene name='pdbligand=P6G:'>P6G</scene>, <scene name='pdbligand=2PE:'>2PE</scene>, <scene name='pdbligand=PG4:'>PG4</scene> and <scene name='pdbligand=1PE:'>1PE</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. This structure supersedes the now removed PDB entry 1P41. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1O57 OCA].  

[[Category: Shin, B S.]]

[[Category: Sinha, S C.]]

[[Category: Smith, J L.]]

[[Category: Tomchick, D R.]]

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