2q7a
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(New page: 200px<br /><applet load="2q7a" size="350" color="white" frame="true" align="right" spinBox="true" caption="2q7a, resolution 2.100Å" /> '''Crystal structure o...)
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Revision as of 08:43, 23 January 2008
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Crystal structure of the cell surface heme transfer protein Shp
Overview
Surface proteins Shr, Shp, and the ATP-binding cassette (ABC) transporter, HtsABC are believed to make up the machinery for heme uptake in, Streptococcus pyogenes. Shp transfers its heme to HtsA, the lipoprotein, component of HtsABC, providing the only experimentally demonstrated, example of direct heme transfer from a surface protein to an ABC, transporter in Gram-positive bacteria. To understand the structural basis, of heme transfer in this system, the heme-binding domain of Shp (Shp(180)), was crystallized, and its structure determined to a resolution of 2.1 A., Shp(180) exhibits an immunoglobulin-like beta-sandwich fold that has been, recently found in other pathogenic bacterial cell surface heme-binding, proteins, suggesting that the mechanisms of heme acquisition are, conserved. Shp shows minimal amino acid sequence identity to these, heme-binding proteins and the structure of Shp(180) reveals a unique, heme-iron coordination with the axial ligands being two methionine, residues from the same Shp molecule. A negative electrostatic surface of, protein structure surrounding the heme pocket may serve as a docking, interface for heme transfer from the more basic outer cell wall heme, receptor protein Shr. The crystal structure of Shp(180) reveals two, exogenous, weakly bound hemins, which form a large interface between the, two Shp(180) molecules in the asymmetric unit. These "extra" hemins form a, stacked pair with a structure similar to that observed previously for free, hemin dimers in aqueous solution. The propionates of the protein-bound, heme coordinate to the iron atoms of the exogenous hemin dimer, contributing to the stability of the protein interface. Gel filtration and, analytical ultracentrifugation studies indicate that both full-length Shp, and Shp(180) are monomeric in dilute aqueous solution.
About this Structure
2Q7A is a Single protein structure of sequence from Streptococcus pyogenes with and as ligands. Known structural/functional Sites: , , , , , , , , , , , and . Full crystallographic information is available from OCA.
Reference
Bis-methionyl coordination in the crystal structure of the heme-binding domain of the streptococcal cell surface protein Shp., Aranda R 4th, Worley CE, Liu M, Bitto E, Cates MS, Olson JS, Lei B, Phillips GN Jr, J Mol Biol. 2007 Nov 23;374(2):374-83. Epub 2007 Aug 31. PMID:17920629
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