tailieunhanh - Báo cáo khoa học: Redox properties of cytochrome P450BM3 measured by direct methods

Cytochrome P450BM3is a self-sufficient fatty acid mono-oxygenase consisting of a diflavin (FAD/FMN) reductase domain and a heme domain fused together in a single polypeptide chain. The multidomain structure makes it an ideal model system for studying the mechanism of electron transfer and for understanding P450 systems in general. Here we report the redox properties of the cyto-chrome P450BM3 wild-type holoenzyme, and its isolated FADreductase andP450 heme domains, when immobilized in a didodecyldimethylammonium bromide film cast on an edge-plane graphite electrode | Eur. J. Biochem. 270 4082-4088 2003 FEBS 2003 doi Redox properties of cytochrome P450BM3 measured by direct methods Barry D. Fleming1 Yanni Tian1 Stephen G. Bell1 Luet-Lok Wong1 Vlada Urlacher2 and H. Allen O. Hill1 1 Department of Chemistry Inorganic Chemistry Laboratory University of Oxford Oxford UK 2Institute of Technical Biochemistry University of Stuttgart Stuttgart Germany Cytochrome P450BM3 is a self-sufficient fatty acid monooxygenase consisting of a diflavin FAD FMN reductase domain and a heme domain fused together in a single polypeptide chain. The multidomain structure makes it an ideal model system for studying the mechanism of electron transfer and for understanding P450 systems in general. Here we report the redox properties of the cytochrome P450BM3 wild-type holoenzyme and its isolated FAD reductase and P450 heme domains when immobilized in a didodecyldimethylammonium bromide film cast on an edge-plane graphite electrode. The holoenzyme showed cyclic voltammetric peaks originating from both the flavin reductase domain and the FeIn Fen redox couple contained in the heme domain with formal potentials of and V with respect to a saturated calomel electrode respectively. When measured in buffer solutions containing the holoenzyme or FAD-reductase domain the reductase response could be maintained for several hours as a result of protein reorganization and refreshing at the didodecyldimethylammonium modified surface. When measured in buffer solution alone the cyclic voltammetric peaks from the reductase domain rapidly diminished in favour of the heme response. Electron transfer from the electrode to the heme was measured directly and at a similarly fast rate ks 221 s-1 to natural biological rates. The redox potential of the FeIII FeII couple increased when carbon monoxide was bound to the reduced heme but when in the presence of substrate s no shift in potential was observed. The reduced heme rapidly .