Spectral and thermodynamic properties of Ag(I), Au(III), Cd(II), Co(II), Fe(III), Hg(II), Mn(II), Ni(II), Pb(II), U(IV), and Zn(II) binding by methanobactin from Methylosinus trichosporium OB3b.
Methanobactin (mb) is a novel chromopeptide that appears to function as the extracellular component of a copper acquisition system in methanotrophic bacteria. To examine this potential physiological role, and to distinguish it from iron binding siderophores, the spectral (UV-visible absorption, circular dichroism, fluorescence, and X-ray photoelectron) and thermodynamic properties of metal binding by mb were examined. In the absence of Cu(II) or Cu(I), mb will bind Ag(I), Au(III), Co(II), Cd(II), Fe(III), Hg(II), Mn(II), Ni(II), Pb(II), U(VI), or Zn(II), but not Ba(II), Ca(II), La(II), Mg(II), and Sr(II). The results suggest metals such as Ag(I), Au(III), Hg(II), Pb(II) and possibly U(VI) are bound by a mechanism similar to Cu, whereas the coordination of Co(II), Cd(II), Fe(III), Mn(II), Ni(II) and Zn(II) by mb differs from Cu(II). Consistent with its role as a copper-binding compound or chalkophore, the binding constants of all the metals examined were less than those observed with Cu(II) and copper displaced other metals except Ag(I) and Au(III) bound to mb. However, the binding of different metals by mb suggests that methanotrophic activity also may play a role in either the solubilization or immobilization of many metals in situ.
Choi
Dong W
DW
Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011-3211, USA. dwon@iastate.edu
Do
Young S
YS
Zea
Corbin J
CJ
McEllistrem
Marcus T
MT
Lee
Sung-W
SW
Semrau
Jeremy D
JD
Pohl
Nicola L
NL
Kisting
Clint J
CJ
Scardino
Lori L
LL
Hartsel
Scott C
SC
Boyd
Eric S
ES
Geesey
Gill G
GG
Riedel
Theran P
TP
Shafe
Peter H
PH
Kranski
Kim A
KA
Tritsch
John R
JR
Antholine
William E
WE
DiSpirito
Alan A
AA
D002942:Circular Dichroism; D007093:Imidazoles / Q000378:metabolism*; D008670:Metals / Q000378:metabolism*; D020581:Methylosinus; D046529:Microscopy, Electron, Transmission; D009842:Oligopeptides / Q000378:metabolism*; D011485:Protein Binding; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
D007093:Imidazoles; D008670:Metals; D009842:Oligopeptides; C491147:methanobactin