Patel, Prakash, 1983-, Song, Lijiang and Challis, Gregory L.. (2010) Distinct extracytoplasmic siderophore binding proteins recognize ferrioxamines and ferricoelichelin in streptomyces coelicolor A3(2). Biochemistry, Vol.49 (No.37). pp. 8033-8042. ISSN 0006-2960

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Abstract

Under iron limitation, the Gram-positive bacterium Streptomyces coelicolor A3(2) excretes three siderophores of the hydroxamate type: desferrioxamine B, desferrioxamine E, and coelichelin. These sequester iron from insoluble ferric hydroxides, and the resulting ferric complexes are believed to be transported into the cell via siderophore-binding proteins (SBPs) associated with ATP-binding cassette (ABC) transporters. Previous studies indicated that some of the genes in the desferrioxamine (des) and coelichelin (cch) biosynthetic clusters encode ABC transporter components required for efficient uptake of ferrioxamine E and ferricoelichelin, respectively, and a third ABC transporter gene cluster (cdt), not associated with siderophore biosynthesis genes, was implicated in the import of ferrioxamine B. In this study, the putative SBPs associated with these three gene clusters, DesE, CchF, and CdtB, were recombinantly overproduced in Escherichia coli and purified to homogeneity, and their binding affinity for cognate siderophores and noncognate siderophores was examined using fluorescence and circular dichroism spectroscopy. DesE was found to bind all of the ferric-tris-hydroxamates tested except ferricoelichelin, while CchF was found to bind only ferricoelichelin efficiently, providing further evidence that the cch cluster is a complete siderophore biosynthesis export uptake gene cluster. The picture was more complicated for CdtB, because it was found to be unstable in solution but was found to bind both ferrioxamine B and ferricoelichelin with high affinity. This was surprising because the cch cluster was previously reported to be necessary for efficient ferricoelichelin uptake. The remarkable specificity of the DesE and CchF proteins for different ferric-tris-hydroxamates raises intriguing questions about the molecular basis of their substrate specificity.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry Q Science > QP Physiology Q Science > QR Microbiology
Divisions:	Faculty of Science > Chemistry Faculty of Science > Molecular Organisation and Assembly in Cells (MOAC)
Library of Congress Subject Headings (LCSH):	Siderophores, Carrier proteins, Streptomyces coelicolor
Journal or Publication Title:	Biochemistry
Publisher:	American Chemical Society
ISSN:	0006-2960
Date:	21 September 2010
Volume:	Vol.49
Number:	No.37
Number of Pages:	10
Page Range:	pp. 8033-8042
Identification Number:	10.1021/bi100451k
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Engineering and Physical Sciences Research Council (EPSRC)
URI:	http://wrap.warwick.ac.uk/id/eprint/5250

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