Oxa1p acts as a general membrane insertion machinery for proteins encoded by mitochondrial DNA

Abstract

Oxa1p is a member of the conserved Oxa1/YidC/Alb3 protein family involved in the membrane insertion of proteins. Oxa1p has been shown previously to directly facilitate the export of the N-terminal domains of membrane proteins across the inner membrane to the intermembrane space of mitochondria. Here we report on a general role of Oxa1p in the membrane insertion of proteins. (i) The function of Oxa1p is not limited to the insertion of membrane proteins that undergo N-terminal tail export; rather, it also extends to the insertion of other polytopic proteins such as the mitochondrially encoded Cox1p and Cox3p proteins. These are proteins whose N-termini are retained in the mitochondrial matrix. (ii) Oxa1p interacts directly with these substrates prior to completion of their synthesis. (iii) The interaction of Oxa1p with its substrates is particularly strong when nascent polypeptide chains are inserted into the inner membrane, suggesting a direct function of Oxa1p in co-translational insertion from the matrix. Taken together, we conclude that the Oxa1 complex represents a general membrane protein insertion machinery in the inner membrane of mitochondria.

Efficient Assembly of Photosystem II in Chlamydomonas reinhardtii Requires Alb3.1p, a Homolog of Arabidopsis ALBINO3

“…This protein is the homolog of mitochondrial Oxa1p and of bacterial YidC, which have been described as integrases involved in the translocation and/or integration of membrane proteins (Moore et al, 2000(Moore et al, , 2003Kuhn et al, 2003). Nevertheless, it was reported that the integral membrane Cox3p and Pf3 coat protein integrate into membranes independently from Oxa1p and YidC, respectively, although with a lower integration efficiency (Hell et al, 2001;Serek et al, 2004).…”

“…Oxa1p is required for the integration of nucleus-and mitochondria-encoded proteins into the inner mitochondrial membrane (Hell et al, 2001), whereas the bacterial YidCp is involved in the cotranslational insertion of inner membrane proteins. The YidC protein has recently been proposed to also be required for the assembly of inserted membrane proteins by cleaning the SecYEG translocase .…”

Heterogeneous Nuclear Ribonucleoprotein K Enhances Insulin-induced Expression of Mitochondrial UCP2 Protein

“…Mitochondria are coated by polysomes that serve to translate mitochondrial proteins from nuclear mRNAs that are recruited to the organelle (37). For example, in yeast and human cells oxa1 mRNA, which encodes a highly conserved mitochondrial inner membrane protein important in the biogenesis of the organelle (38), is enriched in mitochondria-bound polysomes and is likely translated in the vicinity of the organelle (25).…”

One of Two Alb3 Proteins Is Essential for the Assembly of the Photosystems and for Cell Survival in Chlamydomonas

“…In yeast, the inner mitochondrial membrane protein Oxa1p has emerged as an important factor for the assembly of the respiratory chain complexes into the inner mitochondrial membrane (Bonnefoy et al, 1994;Hell et al, 1998Hell et al, , 2001. Oxa1p interacts directly with protein translocation intermediates and facilitates their insertion into the membrane.…”