"The Influence of the Synergistic Anion
on Iron Chelation by Ferric Binding Protein, a Bacterial Transferrin"
Suraj Dhungana, Céline H. Taboy,,
Damon S. Anderson, Kevin G. Vaughan, Philip Aisen, Timothy A.
Mietzner, and Alvin L. Crumbliss
Proc. Natl. Acad. Sci. USA, Vol. 100, Issue 7, 3659-3664, April
1, 2003 (invited article)
Although the presence of an exogenous
anion is a requirement for tight Fe3+ binding by the
bacterial (Neisseria) transferrin nFbp, the identity of the exogenous
anion is not specific in vitro. nFbp was reconstituted as a stable
iron containing protein by using a number of different exogenous
anions [arsenate, citrate, nitrilotriacetate, pyrophosphate, and
oxalate (symbolized by X)] in addition to phosphate, predominantly
present in the recombinant form of the protein. The affinity of
the iron loaded protein for exogenous anion binding at pH 6.5
was found to decrease in the order phosphate > arsenate ~ pyrophosphate
> nitrilotriacetate > citrate ~ oxalate carbonate. Anion influence
on the iron primary coordination sphere through iron binding and
redox potential modulation may have in vivo application as a mechanism
for periplasmic control of iron delivery to the cytosol.
"Chemical Aspects of Siderophore
Mediated Iron Transport"
H. Boukhalfa and A. L. Crumbliss BioMetals, 15, 325 (2002). (invited
review)
In this mini-review we describe selected aspects of the coordination
chemistry relevant to siderophore mediated iron transport and bioavailability.
Specific emphasis is placed on a discussion of in vitro kinetic
and thermodynamic data that are relevant to elucidating possible
in vivo mechanisms for environmental iron acquisition by microbial
cells.
"Fe(III) Coordination Properties of a New Saccharide Based Exocyclic
Trihydroxamate Analogue of Ferrichrome"
S. Dhungana, S. Heggemann, P. Gebhardt, U. Moellmann, and A. L.
Crumbliss
Inorg. Chem., 42, 42-50 (2003)
The coordination chemistry and solution
thermodynamics of a saccharide based synthetic trihydroxamate
analogue of ferrichrome was studied by spectrophotometric and
potentiometric techniques to determine the hydroxamic acid deprotonation
constants, the proton dependent Fe(III) chelation equilibrium
constants and speciation diagram. The redox behavior of the Fe(III)
complex and the Fe(II) chelation constants were determined by
cyclic voltammetry. The relevance of the complex speciation and
redox characteristics to biological iron transport in microbes
is discussed.
The importance of
the coordination chemistry of iron in the biological uses of this
element and the influence of chelation on the biochemistry of
iron are discussed on this tutorial website devoted to free radical
chemistry and biology.
