Erv1 of Arabidopsis thaliana can directly oxidize mitochondrial intermembrane space proteins in the absence of redox-active Mia40

Abstract

BackgroundMany proteins of the mitochondrial intermembrane space (IMS) contain structural disulfide bonds formed by the mitochondrial disulfide relay. In fungi and animals, the sulfhydryl oxidase Erv1 ‘generates’ disulfide bonds that are passed on to the oxidoreductase Mia40, which oxidizes substrate proteins. A different structural organization of plant Erv1 proteins compared to that of animal and fungal orthologs was proposed to explain its inability to complement the corresponding yeast mutant.ResultsHerein, we have revisited the biochemical and functional properties of Arabidopsis thaliana Erv1 by both in vitro reconstituted activity assays and complementation of erv1 and mia40 yeast mutants. These mutants were viable, however, they showed severe defects in the biogenesis of IMS proteins. The plant Erv1 was unable to oxidize yeast Mia40 and rather even blocked its activity. Nevertheless, it was able to mediate the import and folding of mitochondrial proteins.ConclusionsWe observed that plant Erv1, unlike its homologs in fungi and animals, can promote protein import and oxidative protein folding in the IMS independently of the oxidoreductase Mia40. In accordance to the absence of Mia40 in many protists, our study suggests that the mitochondrial disulfide relay evolved in a stepwise reaction from an Erv1-only system to which Mia40 was added in order to improve substrate specificity. Graphical AbstractThe mitochondrial disulfide relay evolved in a step-wise manner from an Erv1-only system. Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-017-0445-8) contains supplementary material, which is available to authorized users.

Oxidative protein folding: state‐of‐the‐art and current avenues of research in plants

“…However, the diversification in the position of the distal/shuttle disulfide may reflect an adaptation of the basic catalytic machinery to specific requirements found in some species. For instance, the human ALR fully complements the yeast erv1 mutant (Sztolsztener et al ., ), whereas the A. thaliana ERV1 counterpart is quite ineffective (Peleh et al ., ).…”

“…An important difference for this molecular interaction is that the distal disulfide in plant ERV1 is situated in the C‐terminal part. Although there is currently no structural information regarding how plant MIA40 and ERV1 interact together, we recently observed that A. thaliana ERV1 does poorly oxidize the yeast MIA40 both in vitro and in vivo (Peleh et al ., ). In fact, the C‐terminal arm containing the cysteine pair forming the distal disulfide in A. thaliana ERV1 does not form the amphipathic helix that is usually found in MIA40‐interacting proteins.…”

“…Although this is not the case in yeast and humans, the structurally different plant ERV1 to some extent might have the capacity to oxidize some proteins, at least the essential ones. Accordingly, we recently determined that A. thaliana ERV1 can bypass the redox function of yeast MIA40 as long as a redox inactive MIA40 is present to trap substrates, but the complementation was partial indicating that the efficiency remains limited (Peleh et al ., ). Hence, a viable alternative is that an unrelated oxidoreductase ensures similar functions to MIA40 in the mitochondrial IMS of plants.…”

Protein Translocation into the Intermembrane Space and Matrix of Mitochondria: Mechanisms and Driving Forces

“…Also in plants, Erv1 can directly bind substrates making Mia40 dispensable. Unfortunately, little is known about the mechanisms of protein translocation in these organisms and other, so far not characterized factors might take over the holdase and foldase function of Mia40 (Carrie et al, 2010 ; Eckers et al, 2013 ; Haindrich et al, 2017 ; Peleh et al, 2017 ).…”

To Mia or not to Mia: stepwise evolution of the mitochondrial intermembrane space disulfide relay

“…The power of this process stems from the oxidizing effect of oxygen. Interestingly, recent work by Peleh et al published in BMC Biology provides evidence that certain sulfhydryl oxidases from the IMS can promote the oxidative folding of substrates independently of any oxidoreductase [ 2 ]. This supports the idea that in the IMS of mitochondria the pathway evolved in a stepwise manner from a pathway utilizing only a sulfhydryl oxidase to one containing both a sulfhydryl oxidase and an oxidoreductase [ 3 ].…”