Expanding the Range of Redox Potentials of the 2Fe-2S Clusters of the Outer Mitochondrial Membrane Protein MitoNEET

Abstract

MitoNEET is a recently discovered outer mitochondrial membrane protein that harbors a 2Fe-2S cluster bound to a unique 3Cys-1His coordination (1). We measured a pH-dependent redox potential with a value near 0 mV at pH 7.0 (Em,7). This value lies intermediate between most low potential 4Cys-coordinated ferredoxin-like (Fd) centers (∼-300 mV) and most high potential 2Cys-2His-coordinated Rieske centers (∼+300 mV) (2). Upon replacing the single His87 ligand with Cys, we obtained an Em,7 near −300 mV closer to that of Fd clusters (Figure). Upon replacing Lys55 located near His87 with Met, Em,7 increases to near +250 mV, closer to that of high potential Rieske clusters (Figure). This shows that there is a large interaction between Lys55 and His87 and that mitoNEET is robust to large changes in the Em,7 of its 2Fe-2S clusters. Thus, we have engineered stable mutant mitoNEET with Em,7 values over a range of almost 600 mV.(1) Paddock et al. (2007) Proc Natl. Acad. Sci USA 104, 14342-14347(2) Meyer (2008) J Biol Inorg Chem 13, 157-170Supported by NIH (GM41637, GM54038 and DK54441).View Large Image | View Hi-Res Image | Download PowerPoint Slide