Iron(III) coordination chemistry of alterobactin A: a siderophore from the marine bacterium Alteromonas luteoviolacea.

TitleIron(III) coordination chemistry of alterobactin A: a siderophore from the marine bacterium Alteromonas luteoviolacea.
Publication TypeJournal Article
Year of Publication2005
AuthorsHolt PD, Reid RR, Lewis BL, Luther GW, Butler A
JournalInorg Chem
Volume44
Issue21
Pagination7671-7
Date Published2005 Oct 17
ISSN0020-1669
KeywordsAlteromonas, Drug Stability, Ferric Compounds, Kinetics, Models, Molecular, Molecular Structure, Peptides, Cyclic, Siderophores
Abstract

Alterobactin A is a siderophore produced by the oceanic bacterium Alteromonas luteoviolacea. The thermodynamic stability constant of the ferric alterobactin A (Alt-A) complex was estimated from electrochemical measurements on the basis of a previously reported linear relationship between the reduction potentials and the pH-independent stability constants for known iron(III) complexes. The reduction potential of the ferric alterobactin A complex determined by square wave voltammetry is -0.972 V vs SCE and reversible, corresponding to a thermodynamic stability constant of 10(51+/-2). Potentiometric titration of Fe(III)-Alt-A shows the release of six protons on complexation of Fe(III) to Alt-A. The 1H NMR resonances of the Ga(III)-Alt-A complex show that the C-4, C-5, and C-6 catecholate protons and the C(alpha) and C(beta) protons of both beta-hydroxyaspartate moieties are shifted downfield relative to the free ligand, which along with the potentiometric titration data is consistent with a complex in which Fe(III) is coordinated by both catecholate oxygen atoms and both oxygen atoms of each beta-hydroxyaspartate. The UV-vis spectrum of Fe(III)-Alt-A is invariant over the pH range 4-9, indicating the coordination does not change over a wide pH range. In addition, in the absence of a coordinated metal ion, the serine ester of Alt-A hydrolyzes forming Alt-B.

DOI10.1021/ic0512072
Alternate JournalInorg Chem
PubMed ID16212394
Grant ListGM 38130 / GM / NIGMS NIH HHS / United States