1lm2

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NMR structural characterization of the reduction of chromium(VI) to chromium(III) by cytochrome c7

Overview

The redox reaction between CrO(4)(2-) and the fully reduced three-heme, cytochrome c(7) from Desulfuromonas acetoxidans to give chromium(III) and, the fully oxidized protein has been followed by NMR spectroscopy. The, hyperfine coupling between the oxidized protein protons and chromium(III), which remains bound to the protein, gives rise to line-broadening effects, on the NMR resonances that can be transformed into proton-metal distance, restraints. Structure calculations based on these unconventional, constraints allowed us to demonstrate that chromium(III) binds at a unique, site and to locate it on the protein surface. The metal ion is located 7.9, +/- 0.4 A from the iron of heme IV, 16.3 +/- 0.7 A from the iron of heme, III, and 22.5 +/- 0.5 A from the iron of heme I. Shift changes caused by, the presence of unreactive MoO(4)(2-), a CrO(4)(2-) analogue, indicate the, involvement of the same protein area in the anion binding. The titration, of the oxidation of cytochrome c(7) shows a detailed mechanism of action., The presence of a specific binding site supports the hypothesis of the, biological role of this cytochrome as a metal reductase.

About this Structure

1LM2 is a Single protein structure of sequence from Desulfuromonas acetoxidans with CR and HEC as ligands. Full crystallographic information is available from OCA.

Reference

The metal reductase activity of some multiheme cytochromes c: NMR structural characterization of the reduction of chromium(VI) to chromium(III) by cytochrome c(7)., Assfalg M, Bertini I, Bruschi M, Michel C, Turano P, Proc Natl Acad Sci U S A. 2002 Jul 23;99(15):9750-4. Epub 2002 Jul 15. PMID:12119407

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