Structural Basis for Phosphate Stabilization of the Uniquely Coordinated 2Fe-2S Cluster of the Outer Mitochondrial Membrane Protein MitoNEET.∗

Abstract

MitoNEET is the first outer mitochondrial membrane protein shown to contain a pH labile redox active 2Fe-2S cluster (1). Additionally, we found that phosphate at physiological concentrations (10 mM) stabilized the cluster from release by ∼10-fold over a broad pH range from 5.0 ≤ pH ≤ 7.5. The structure obtained using phosphate buffer (pH 7.0, 1.75A diffraction, Rfactor=18%) showed the presence of a bound phosphate anion interacting with His87, a key residue in cluster release (1). The phosphate also interacts with the N-terminus of a symmetry-related dimer (Figure). None of these interactions were previously reported (2-4). We attribute the increased stability to the novel interactions, suggesting that the rate of cluster release could be modulated by interaction with a phosphate or phosphate moiety, such as a phosphorylated protein or peptide.(1) Wiley et al. (2007) J Biol Chem. 282, 23745-23749.(2) Paddock et al. (2007) Proc Natl. Acad. Sci USA 104, 14342-14347.(3) Lin et al (2007) Proc. Natl. Acad. Sci USA 104, 14640-14645.(4) Hou et al (2007) J Mol Biol 282, 33242-33246.∗Supported by NIH GM 41637,GM54038 and DK54441.View Large Image | View Hi-Res Image | Download PowerPoint Slide