TY - JOUR
T1 - Structural dependence of Mn complexation by siderophores
T2 - Donor group dependence on complex stability and reactivity
AU - Harrington, James M.
AU - Parker, Dorothy L.
AU - Bargar, John R.
AU - Jarzecki, Andrzej A.
AU - Tebo, Bradley M.
AU - Sposito, Garrison
AU - Duckworth, Owen W.
N1 - Funding Information:
We are grateful for support received from the National Science Foundation Geobiology and Low-Temperature Geochemistry Program (award number EAR-0921313), Molecular and Cellular Biosciences (MCB-0630355) and the Collaborative Research Activities in Environmental Molecular Science (CRAEMS) program (CHE-0089208). We thank Joe Rogers and Jeff Maske for help during data collection at the synchrotron. Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. The SSRL Structural Molecular Biology Program is supported by the Department of Energy, Office of Biological and Environmental Research, and by the National Institutes of Health, National Center for Research Resources, Biomedical Technology Program.
PY - 2012/7/1
Y1 - 2012/7/1
N2 - Siderophores traditionally have been viewed as solely being involved in the biogeochemical cycling of Fe(III). This paradigm, however, ignores the diverse roles siderophores may play in the cycling of other trace metals, such as Mn, Co, Mo, and V. Recent work has shown that siderophores form complexes with high stability constants with Mn(III), which are in some cases higher than that of the corresponding Fe(III) complex. Herein, we report on a structural analysis of the dissolved Fe(III)- and Mn(III)-siderophore complexes of rhizoferrin and two pyoverdin-type siderophores using X-ray spectroscopic techniques. Additionally, the stability constants of the Mn(III)-pyoverdin PaA and Mn(III)-rhizoferrin complexes have been quantified as log β 111=47.5±0.3 and log β 110=29.8±0.3, respectively. Comparisons of thermodynamic stability and solution structures of Fe(III)- and Mn(III)-complexes with a variety of siderophores demonstrate the relationship between donor group identity, siderophore structure, and strength of complex formation. Rhizoferrin and two mixed-moiety pyoverdins bind with a higher affinity for Mn(III) than Fe(III), possibly because of binding moiety composition which makes them better able to accommodate Jahn-Teller distortion. In contrast, Fe(III) forms complexes of higher relative stability with siderophores that contain hydroxamate and catecholate moieties, more rigid donor groups that form five-membered chelate rings.
AB - Siderophores traditionally have been viewed as solely being involved in the biogeochemical cycling of Fe(III). This paradigm, however, ignores the diverse roles siderophores may play in the cycling of other trace metals, such as Mn, Co, Mo, and V. Recent work has shown that siderophores form complexes with high stability constants with Mn(III), which are in some cases higher than that of the corresponding Fe(III) complex. Herein, we report on a structural analysis of the dissolved Fe(III)- and Mn(III)-siderophore complexes of rhizoferrin and two pyoverdin-type siderophores using X-ray spectroscopic techniques. Additionally, the stability constants of the Mn(III)-pyoverdin PaA and Mn(III)-rhizoferrin complexes have been quantified as log β 111=47.5±0.3 and log β 110=29.8±0.3, respectively. Comparisons of thermodynamic stability and solution structures of Fe(III)- and Mn(III)-complexes with a variety of siderophores demonstrate the relationship between donor group identity, siderophore structure, and strength of complex formation. Rhizoferrin and two mixed-moiety pyoverdins bind with a higher affinity for Mn(III) than Fe(III), possibly because of binding moiety composition which makes them better able to accommodate Jahn-Teller distortion. In contrast, Fe(III) forms complexes of higher relative stability with siderophores that contain hydroxamate and catecholate moieties, more rigid donor groups that form five-membered chelate rings.
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U2 - 10.1016/j.gca.2012.04.006
DO - 10.1016/j.gca.2012.04.006
M3 - Article
AN - SCOPUS:84861685080
SN - 0016-7037
VL - 88
SP - 106
EP - 119
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
ER -