COMPLETE STRUCTURE OF THE 11-SUBUNIT BOVINE MITOCHONDRIAL CYTOCHROME BC(1) COMPLEX

Mitochondrial cytochrome bc(1) complex performs two functions: It is a respiratory multienzyme complex and it recognizes a mitochondrial tar geting presequence. Refined crystal structures of the 11-subunit bc(1) complex from bovine heart reveal full views of this bifunctional enzy me. The ''Rieske'' iron-sulfur protein subunit shows significant confo rmational changes in different crystal forms, suggesting a new electro n transport mechanism of the enzyme. The mitochondrial targeting prese quence of the ''Rieske'' protein (subunit 9) is lodged between the two ''core'' subunits at the matrix side of the complex. These ''core'' s ubunits are related to the matrix processing peptidase, and the struct ure unveils how mitochondrial targeting presequences are recognized.