PMID:15839704
| Citation |
Tabares, LC, Cortez, N, Agalidis, I and Un, S (2005) Temperature-dependent coordination in E. coli manganese superoxide dismutase. J. Am. Chem. Soc. 127:6039-47 |
|---|---|
| Abstract |
Two different temperature dependences of the manganese(II) high-field electron paramagnetic resonance spectrum of manganese superoxide dismutase from E. coli were observed. In the 25-200 K range, the zero-field interaction steadily decreased with increasing temperature. This was likely due to the thermal expansion of the protein. From these results, it was possible to deduce an approximately r(-)(2.5) dependence of Mn(II) zero-field interaction on ligand-metal distance. At temperatures above 240 K, a distinct six-line component was detected, the amplitude of which decreased with increasing temperature. On the basis of similarities to the six-line spectrum observed for the azide-complexed E. coli manganese superoxide dismutase, the newly detected six-line spectrum was assigned to a hexacoordinate Mn(II) center resulting from the coordination of a nearby water molecule to the normally five-coordinate center. The changes in enthalpy and entropy characterizing the hexacoordinate-pentacoordinate equilibrium in the 240-268 K range were -5 kcal/mol and -24 cal/mol.K, respectively. The structural implications of the zero-field parameters of the newly found hexacoordinate form in comparison to those of the Mn(II) centers in concanavalin-A and manganese-containing R. spheroides photosynthetic reaction centers and the values predicted by the superposition model are discussed. |
| Links |
PubMed Online version:10.1021/ja047007r |
| Keywords |
Cold Temperature; Electron Spin Resonance Spectroscopy; Escherichia coli/enzymology; Iron/chemistry; Manganese/chemistry; Models, Molecular; Superoxide Dismutase/chemistry; Temperature |
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