The Rieske Iron-Sulfur Protein: Import and Assembly into the Cytochrome Complex of Yeast Mitochondria

Laura Conte,Vincenzo Zara

doi:10.1155/2011/363941

Abstract

The Rieske iron-sulfur protein, one of the catalytic subunits of the cytochrome bc 1 complex, is involved in electron transfer at the level of the inner membrane of yeast mitochondria. The Rieske iron-sulfur protein is encoded by nuclear DNA and, after being synthesized in the cytosol, is imported into mitochondria with the help of a cleavable N-terminal presequence. The imported protein, besides incorporating the 2Fe-2S cluster, also interacts with other catalytic and non-catalytic subunits of the cytochrome bc 1 complex, thereby assembling into the mature and functional respiratory complex. In this paper, we summarize the most recent findings on the import and assembly of the Rieske iron-sulfur protein into Saccharomyces cerevisiae mitochondria, also discussing a possible role of this protein both in the dimerization of the cytochrome bc 1 complex and in the interaction of this homodimer with other complexes of the mitochondrial respiratory chain.

Highlights

The Rieske iron-sulfur protein (Rip1p or ISP) is one of the catalytic subunits of the cytochrome bc1 complex
ISP strictly cooperates with cytochrome b and cytochrome c1 in the electron transfer catalyzed by the mitochondrial cytochrome bc1 complex
This intermembrane space domain is connected by a short amino acid linker to the hydrophobic N-terminal α-helix, which is inserted into the inner mitochondrial membrane

Summary

Introduction

The Rieske iron-sulfur protein (Rip1p or ISP) is one of the catalytic subunits of the cytochrome bc complex ( known as complex III of the mitochondrial respiratory chain) This respiratory enzyme assembles as a mature and functional homodimer in the inner membrane of mitochondria; besides ISP, it incorporates two further catalytic subunits, cytochrome b and cytochrome c1, and seven noncatalytic subunits (core protein 1 and core protein 2, Qcr6p, Qcr7p, Qcr8p, Qcr9p, Qcr10p). These last subunits are named “supernumerary” because they are absent in some bacterial equivalents of cytochrome bc complex [1, 2]. It is possible that ISP, besides representing an obligatory component for the redox activity of the bc complex, may play a role in building up the mature and functional complex III in the mitochondrial membranes

Structural Characteristics of ISP in the Cytochrome bc1 Complex

Import and Maturation of ISP into Yeast Mitochondria

Assembly of ISP into the Cytochrome bc1 Complex

Insertion of ISP into a Core Structure of the Cytochrome bc1 Complex

Concluding Remarks

Abbreviations