Specificity of Staphyloferrin B Recognition by the SirA Receptor from Staphylococcus aureus
Journal Article
·
· Journal of Biological Chemistry
- Univ. of British Columbia, Vancouver, BC (Canada). Life Sciences Inst., Dept. of Microbiology and Immunology; DOE/OSTI
- Univ. of Western Ontario, London, ON (Canada). Dept. of Microbiology and Immunology
- Univ. of British Columbia, Vancouver, BC (Canada). Life Sciences Inst., Dept. of Microbiology and Immunology
Many organisms use sophisticated systems to acquire growth-limiting iron. Iron limitation is especially apparent in bacterial pathogens of mammalian hosts where free iron concentrations are physiologically negligible. A common strategy is to secrete low molecular weight iron chelators, termed siderophores, and express high affinity receptors for the siderophore-iron complex. Staphylococcus aureus, a widespread pathogen, produces two siderophores, staphyloferrin A (SA) and staphyloferrin B (SB). We have determined the crystal structure of the staphyloferrin B receptor, SirA, at high resolution in both the apo and Fe(III)-SB (FeSB)-bound forms. SirA, a member of the class III binding protein family of metal receptors, has N- and C-terminal domains, each composed of mainly a β-stranded core and α-helical periphery. The domains are bridged by a single α-helix and together form the FeSB binding site. SB coordinates Fe(III) through five oxygen atoms and one nitrogen atom in distorted octahedral geometry. SirA undergoes conformational change upon siderophore binding, largely securing two loops from the C-terminal domain to enclose FeSB with a low nanomolar dissociation constant. The staphyloferrin A receptor, HtsA, homologous to SirA, also encloses its cognate siderophore (FeSA); however, the largest conformational rearrangements involve a different region of the C-terminal domain. FeSB is uniquely situated in the binding pocket of SirA with few of the contacting residues being conserved with those of HtsA interacting with FeSA. Although both SirA and HtsA bind siderophores from the same α-hydroxycarboxylate class, the unique structural features of each receptor provides an explanation for their distinct specificity.
- Research Organization:
- SLAC National Accelerator Laboratory, Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
- Sponsoring Organization:
- Canadian Institutes of Health Research (CIHR); Michael Smith Foundation for Health Research; National Center for Research Resources (NCRR); National Institute of General Medical Sciences (NIGMS); National Institutes of Health (NIH); Natural Sciences and Engineering Research Council of Canada (NSERC); USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Biological and Environmental Research (BER)
- Grant/Contract Number:
- AC02-76SF00515
- OSTI ID:
- 1625072
- Journal Information:
- Journal of Biological Chemistry, Journal Name: Journal of Biological Chemistry Journal Issue: 45 Vol. 285; ISSN 0021-9258
- Publisher:
- American Society for Biochemistry and Molecular BiologyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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