PrrC from Rhodobacter sphaeroides, a homologue of eukaryotic Sco proteins, is a copper-binding protein and may have a thiol-disulfide oxidoreductase activity

McEwan, A. G., Lewin, A., Davy, S. L., Boetzel, R., Leech, A., Walker, D. , Wood, T. and Moore, G. R. (2002) PrrC from Rhodobacter sphaeroides, a homologue of eukaryotic Sco proteins, is a copper-binding protein and may have a thiol-disulfide oxidoreductase activity. FEBS Letters, 518(1-3), pp. 10-16. (doi:10.1016/S0014-5793(02)02532-2)

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Publisher's URL: http://dx.doi.org/10.1016/S0014-5793(02)02532-2

Abstract

PrrC from <i>Rhodobacter sphaeroides</i> provides the signal input to a two-component signal transduction system that senses changes in oxygen tension and regulates expression of genes involved in photosynthesis (Eraso, J.M. and Kaplan, S. (2000) Biochemistry 39, 2052-2062; Oh, J.-I. and Kaplan, S. (2000) EMBO J. 19, 4237-4247). It is also a homologue of eukaryotic Sco proteins and each has a C-x-x-x-C-P sequence. In mitochondrial Sco proteins these cysteines appear to be essential for the biogenesis of the Cu<sub>A</sub> centre of respiratory cytochrome oxidase. Overexpression and purification of a water-soluble and monomeric form of PrrC has provided sufficient material for a chemical and spectroscopic study of the properties of the four cysteine residues of PrrC, and its ability to bind divalent cations, including copper. PrrC expressed in the cytoplasm of <i>Escherichia coli</i> binds Ni<sup>2+</sup> tightly and the data are consistent with a mononuclear metal site. Following removal of Ni<sup>2+</sup> and formation of renatured metal-free rPrrC (apo-PrrC), Cu<sup>2+</sup> could be loaded into the reduced form of PrrC to generate a protein with a distinctive UV-visible spectrum, having absorbance with a <i>λ</i><sub>m</sub>ax of 360 nm. The copper:PrrC ratio is consistent with the presence of a mononuclear metal centre. The cysteines of metal-free PrrC oxidise in the presence of air to form two intramolecular disulfide bonds, with one pair being extremely reactive. The cysteine thiols with extreme O<sub>2</sub> sensitivity are involved in copper binding in reduced PrrC since the same copper-loaded protein could not be generated using oxidised PrrC. Thus, it appears that PrrC, and probably Sco proteins in general, could have both a thiol-disulfide oxidoreductase function and a copper-binding role.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Walker, Professor Daniel
Authors: McEwan, A. G., Lewin, A., Davy, S. L., Boetzel, R., Leech, A., Walker, D., Wood, T., and Moore, G. R.
College/School:College of Medical Veterinary and Life Sciences
College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
Journal Name:FEBS Letters
Publisher:Elsevier BV
ISSN:0014-5793
ISSN (Online):1873-3468
Published Online:09 April 2002

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