2iyn
The co-factor-induced pre-active conformation in PhoB
Structural highlights
FunctionPHOB_ECOLI This protein is a positive regulator for the phosphate regulon. Transcription of this operon is positively regulated by PhoB and PhoR when phosphate is limited. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedPhoB 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. 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[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
| ||||||||||||||||||||
