2cn4
From Proteopedia
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THE CRYSTAL STRUCTURE OF THE SECRETED DIMERIC FORM OF THE HEMOPHORE HASA REVEALS A DOMAIN SWAPPING WITH AN EXCHANGED HEME LIGAND
Overview
To satisfy their iron needs, several Gram-negative bacteria use a heme, uptake system involving an extracellular heme-binding protein called, hemophore. The function of the hemophore is to acquire free or, hemoprotein-bound heme and to transfer it to HasR, its specific outer, membrane receptor, by protein-protein interaction. The hemophore HasA, secreted by Serratia marcescens, an opportunistic pathogen, was the first, to be identified and is now very well characterized. HasA is a monomer, that binds one b heme with strong affinity. The heme in HasA is highly, exposed to solvent and coordinated by an unusual pair of ligands, a, histidine and a tyrosine. Here, we report the identification, the, characterization and the X-ray structure of a dimeric form of HasA from S., marcescens: DHasA. We show that both monomeric and dimeric forms are, secreted in iron deficient conditions by S. marcescens. The crystal, structure of DHasA reveals that it is a domain swapped dimer. The overall, structure of each monomeric subunit of DHasA is very similar to that of, HasA but formed by parts coming from the two different polypeptide chains, involving one of the heme ligands. Consequently DHasA binds two heme, molecules by residues coming from both polypeptide chains. We show here, that, while DHasA can bind two heme molecules, it is not able to deliver, them to the receptor HasR. However, DHasA can efficiently transfer its, heme to the monomeric form that, in turn, delivers it to HasR. We assume, that DHasA can function as a heme reservoir in the hemophore system.
About this Structure
2CN4 is a Single protein structure of sequence from Serratia marcescens with PO4 and HEM as ligands. Known structural/functional Site: . Full crystallographic information is available from OCA.
Reference
The crystal structure of the secreted dimeric form of the hemophore HasA reveals a domain swapping with an exchanged heme ligand., Czjzek M, Letoffe S, Wandersman C, Delepierre M, Lecroisey A, Izadi-Pruneyre N, J Mol Biol. 2007 Jan 26;365(4):1176-86. Epub 2006 Oct 25. PMID:17113104
Page seeded by OCA on Tue Dec 18 19:29:41 2007
