Dual Function of Sdh3 in the Respiratory Chain and TIM22 Protein Translocase of the Mitochondrial Inner Membrane

SummaryThe mitochondrial inner membrane harbors the complexes of the respiratory chain and translocase complexes for precursor proteins. We have identified a further subunit of the carrier translocase (TIM22 complex) that surprisingly is identical to subunit 3 of respiratory complex II, succinate dehydrogenase (Sdh3). The membrane-integral protein Sdh3 plays specific functions in electron transfer in complex II. We show by genetic and biochemical approaches that Sdh3 also plays specific functions in the TIM22 complex. Sdh3 forms a subcomplex with Tim18 and is involved in biogenesis and assembly of the membrane-integral subunits of the TIM22 complex. We conclude that the assembly of Sdh3 with different partner proteins, Sdh4 and Tim18, recruits it to two different mitochondrial membrane complexes with functions in bioenergetics and protein biogenesis, respectively.

Graphical AbstractFigure optionsDownload high-quality image (181 K)Download as PowerPoint slideHighlights
► Subunit of mitochondrial respiratory chain functions in protein import
► Succinate dehydrogenase subunit 3 (Sdh3) is a subunit of TIM22 protein translocase
► Sdh4 and Tim18 recruit Sdh3 to two different membrane protein complexes
► Membrane module of respiratory complex as evolutionary building block for translocase