2g5g
From Proteopedia
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Cofacial heme binding to ChaN of Campylobacter jejuni
Overview
Campylobacter jejuni is a leading bacterial cause of food-borne illness in, the developed world. Like most pathogens, C. jejuni requires iron that, must be acquired from the host environment. Although the iron preference, of the food-borne pathogen C. jejuni is not established, this organism, possesses heme transport systems to acquire iron. ChaN is an, iron-regulated lipoprotein from C. jejuni proposed to be associated with, ChaR, an outer-membrane receptor. Mutation of PhuW, a ChaN orthologue in, Pseudomonas aeruginosa, compromises growth on heme as a sole iron source., The crystal structure of ChaN, determined to 1.9 A resolution reveals that, ChaN is comprised of a large parallel beta-sheet with flanking, alpha-helices and a smaller domain consisting of alpha-helices., Unexpectedly, two cofacial heme groups ( approximately 3.5 A apart with an, inter-iron distance of 4.4 A) bind in a pocket formed by a dimer of ChaN, monomers. Each heme iron is coordinated by a single tyrosine from one, monomer, and the propionate groups are hydrogen bonded by a histidine and, a lysine from the other monomer. Sequence analyses reveal that these, residues are conserved among ChaN homologues from diverse bacterial, origins. Electronic absorption and electron paramagnetic resonance (EPR), spectroscopy are consistent with heme binding through tyrosine, coordination by ChaN in solution yielding a high-spin heme iron structure, in a pH-dependent equilibrium with a low-spin species. Analytical, ultracentrifugation demonstrates that apo-ChaN is predominantly monomeric, and that dimerization occurs with heme binding such that the stability, constant for dimer formation increases by 60-fold.
About this Structure
2G5G is a Single protein structure of sequence from Campylobacter jejuni subsp. jejuni with as ligand. Full crystallographic information is available from OCA.
Reference
Cofacial heme binding is linked to dimerization by a bacterial heme transport protein., Chan AC, Lelj-Garolla B, I Rosell F, Pedersen KA, Mauk AG, Murphy ME, J Mol Biol. 2006 Oct 6;362(5):1108-19. Epub 2006 Aug 4. PMID:16950397
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