Mia40 Is Optimized for Function in Mitochondrial Oxidative Protein Folding and Import

• Published in: ACS chemical biology 2014-09, Vol.9 (9), p.2049-2057
• Main Authors: Koch, Johanna R, Schmid, Franz X
• Format: Article
• Language: English
• Subjects: Catalytic Domain; Cation Transport Proteins - chemistry; Cation Transport Proteins - metabolism; Cysteine - metabolism; Disulfides - chemistry; Dithionitrobenzoic Acid - chemistry; Dithionitrobenzoic Acid - metabolism; Escherichia coli Proteins - chemistry; Escherichia coli Proteins - metabolism; Mitochondrial Membrane Transport Proteins - chemistry; Mitochondrial Membrane Transport Proteins - metabolism; Models, Molecular; Molecular Chaperones - chemistry; Molecular Chaperones - metabolism; Protein Conformation; Protein Disulfide-Isomerases - chemistry; Protein Disulfide-Isomerases - metabolism; Protein Folding; Protein Stability; Protein Transport; Saccharomyces cerevisiae Proteins - chemistry; Saccharomyces cerevisiae Proteins - metabolism
• ISSN: 1554-8929; 1554-8937
• DOI: 10.1021/cb500408n

Mia40 catalyzes oxidative protein folding in mitochondria. It contains a unique catalytic CPC dithiol flanked by a hydrophobic groove, and unlike other oxidoreductases, it forms long-lived mixed disulfides with substrates. We show that this distinctive property originates neither from particular properties of mitochondrial substrates nor from the CPC motif of Mia40. The catalytic cysteines of Mia40 display unusually low chemical reactivity, as expressed in conventional pK values and reduction potentials. The stability of the mixed disulfide intermediate is coupled energetically with hydrophobic interactions between Mia40 and the substrate. Based on these properties, we suggest a mechanism for Mia40, where the hydrophobic binding site is employed to select a substrate thiol for forming the initial mixed disulfide. Its long lifetime is used to retain partially folded proteins in the mitochondria and to direct folding toward forming the native disulfide bonds.