Conserved Negative Charges in the Transmembrane Segments of Subunit K of the NADH:Ubiquinone Oxidoreductase Determine Its Dependence on YidC for Membrane Insertion

Claire E. Price,Arnold J.M. Driessen

doi:10.1074/jbc.m109.051128

Abstract

All members of the Oxa1/Alb3/YidC family have been implicated in the biogenesis of respiratory and energy transducing proteins. In Escherichia coli, YidC functions together with and independently of the Sec system. Although the range of proteins shown to be dependent on YidC continues to increase, the exact role of YidC in insertion remains enigmatic. Here we show that YidC is essential for the insertion of subunit K of the NADH:ubiquinone oxidoreductase and that the dependence is due to the presence of two conserved glutamate residues in the transmembrane segments of subunit K. The results suggest a model in which YidC serves as a membrane chaperone for the insertion of the less hydrophobic, negatively charged transmembrane segments of NuoK.

Highlights

In Escherichia coli the inner membrane contains essential energy transducing complexes such as components of the electron transport chain
We show that YidC is essential for the insertion of subunit K of the NADH: ubiquinone oxidoreductase and that the dependence is due to the presence of two conserved glutamate residues in the transmembrane segments of subunit K
We showed that YidC depletion in E. coli resulted in a cessation of growth under anaerobic conditions and that this growth defect may be in part due to reduced levels of the complex I homolog in bacteria, the NADH:ubiquinone reductase, or NADH dehydrogenase I, in the membrane [21]

Summary

Introduction

In Escherichia coli the inner membrane contains essential energy transducing complexes such as components of the electron transport chain. Oxa (oxidase assembly) from yeast was the first member of this family to be described [6, 7] It was originally identified as an essential factor for the biogenesis of respiratory complexes in the mitochondrion, for the insertion of subunits of the cytochrome bc oxidase and ATP synthase [8]. For example Oxa proteins appear to have a varying role in the biogenesis of respiratory complexes I, III, IV, and V as illustrated by studies in Neurospora crassa, [15], Podospora anseria [16], HEK293 cells [17], and Saccharomyces cerevisiae (6, 7, 18 –20) This highlights that the general function of Oxa1/Alb3/YidC family proteins is known, each member plays a specific and in some cases yet to be identified role in the biogenesis of respiratory proteins. We found that in vitro synthesized NuoK requires both SecYEG and YidC for insertion and that two conserved negative charges in TMSs 2 and 3 determine the dependence of NuoK on YidC for insertion

Objectives

Methods

Conclusion