Crystal Structures of Deoxy and CO-Bound bjFixLH Reveal Details of Ligand Recognition and Signaling
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- 作者：Jason Key and Keith Moffat
- 刊名：Biochemistry
- 出版年：2005
- 出版时间：March 29, 2005
- 年：2005
- 卷：44
- 期：12
- 页码：4627 - 4635
- 全文大小：1532K
- 年卷期：v.44,no.12(March 29, 2005)
- ISSN：1520-4995
文摘
Rhizobia directly regulate the expression of genes required for symbiotic nitrogen fixation inresponse to oxygen concentration via the sensor protein FixL. The N-terminal PAS domain of FixL containsa histidine-coordinated heme and regulates the activity of its effector domain, a C-terminal histidine kinase,in response to binding of oxygen and other ligands at the heme. To further investigate ligand-inducedinhibition of FixL, we have determined the crystal structures of the heme domain in both the deoxy stateand bound to carbon monoxide, a weak inhibitor of FixL kinase activity. Structures collected at roomtemperature are presented in each state from two crystallographic space groups at 1.8 and 2 Å resolution.These structures reveal displacement of the residues of the H
and I strands by Leu236 upon CO binding,and this structural change propagates more than 15 Å to a region of the structure implicated in signaltransduction in PAS proteins. Displacement of residues Ile215, Ile216, and Gly217 in the FG loop is alsoevident, accompanied by the movement of heme propionate 6 upon change in iron ligation. CO bindingincreases the temperature factors in the FG loop of the protein and disorders the side chain of Arg206, aconserved residue involved in the FG loop switch mechanism. We relate these results to structural changesin other PAS sensor domains and their involvement in catalytic control.
and I strands by Leu236 upon CO binding,and this structural change propagates more than 15 Å to a region of the structure implicated in signaltransduction in PAS proteins. Displacement of residues Ile215, Ile216, and Gly217 in the FG loop is alsoevident, accompanied by the movement of heme propionate 6 upon change in iron ligation. CO bindingincreases the temperature factors in the FG loop of the protein and disorders the side chain of Arg206, aconserved residue involved in the FG loop switch mechanism. We relate these results to structural changesin other PAS sensor domains and their involvement in catalytic control.