2iyn

From Proteopedia

Revision as of 17:31, 18 December 2007

THE CO-FACTOR-INDUCED PRE-ACTIVE CONFORMATION IN PHOB

Overview

PhoB is an Escherichia coli transcription factor from a two-component, signal transduction system that is sensitive to limiting environmental, phosphate conditions. It consists of an N-terminal receiver domain (RD), and a C-terminal DNA-binding domain. The protein is activated upon, phosphorylation at the RD, an event that depends on Mg(2+) binding. The, structure of PhoB RD in complex with Mg(2+) is presented, which shows, three protomers in the asymmetric unit that interact across two different, surfaces. One association is symmetric and has been described as a, non-active dimerization contact; the other involves the, alpha4-beta5-alpha5 interface and recalls the contact found in activated, PhoB. However, here this last interaction is not perfectly symmetric and, helix alpha4, which in the activated molecule undergoes a helical shift, becomes strongly destabilized in one of the interacting monomers. All, protomers bind the cation in a similar manner but, interestingly, at the, prospective binding site for the phosphate moiety the side chains of, either Glu88 (in helix alpha4) or Trp54 alternate and interact with, active-site atoms. When Glu88 is inside the cavity, helix alpha4 is, arranged similarly to the unliganded wild-type structure. However, if, Trp54 is present, the helix loses its contacts with the active-site cavity, and vanishes. Accordingly, the presence of Trp54 in the active site, induces a flexible state in helix alpha4, potentially allowing a helical, shift that phosphorylation would eventually stabilize.

About this Structure

2IYN is a Single protein structure of sequence from Escherichia coli with MG as ligand. Known structural/functional Site: . Full crystallographic information is available from OCA.

Reference

The cofactor-induced pre-active conformation in PhoB., Sola M, Drew DL, Blanco AG, Gomis-Ruth FX, Coll M, Acta Crystallogr D Biol Crystallogr. 2006 Sep;62(Pt 9):1046-57. Epub 2006, Aug 19. PMID:16929106

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