Christoph Mårtensson

Abstract

The translocase of the outer membrane (TOM complex) forms the entry gate for the majority of mitochondrial precursor proteins. Subsequently, specific protein complexes sort the precurcor proteins into the different subcompartments. The presequence translocase (TIM23 complex) transport proteins across and into the inner membrane. The TIM23 complex cooperates with the presequence-translocase associated motor (PAM) for transport into the mitochondrial matrix. The carrier translocase (TIM22 complex) inserts proteins into the inner membrane. The activity of the respiratory chain generates a membrane potential that drives both protein import pathways. The MIA machinery transports cysteine-rich proteins into the intermembrane space. Outer membrane proteins with β-barrel structure are first transported across the TOM machinery and then inserted into the outer membrane by the sorting and assembly machinery (SAM complex). Finally, the mitochondrial import machinery (MIM) promotes biogenesis of outer membrane proteins with a-helical membrane anchor. Whereas function and composition of the protein machineries are at least partly understood the mechanisms to remove defective or unassembled components of protein translocases are poorly understood. This project aims to investigate mechanisms of the quality control of the mitochondrial protein translocases.

Methods

• Yeast cell culture
• Isolation of Mitochondria
• Cell free translation of membrane proteins
• In vitro protein import into yeast mitochondria
• Cell culture
• Blue native PAGE
• Affinity purification