Mgr2 Functions as Lateral Gatekeeper for Preprotein Sorting in the Mitochondrial Inner Membrane

• Published in: Molecular cell Vol. 56; no. 5; pp. 641 - 652
• Main Authors: Ieva, Raffaele, Schrempp, Sandra G., Opaliński, Łukasz, Wollweber, Florian, Höß, Philipp, Heißwolf, Anna K., Gebert, Michael, Zhang, Ying, Guiard, Bernard, Rospert, Sabine, Becker, Thomas, Chacinska, Agnieszka, Pfanner, Nikolaus, van der Laan, Martin
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 04.12.2014
• Subjects: GTP-Binding Proteins - metabolism; Membrane Proteins - genetics; Membrane Proteins - metabolism; Membrane Transport Proteins - metabolism; Methotrexate - pharmacology; Mitochondria - metabolism; Mitochondria - ultrastructure; Mitochondrial Membranes - metabolism; Mitochondrial Proteins - metabolism; Protein Transport - drug effects; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2014.10.010

The majority of preproteins destined for mitochondria carry N-terminal presequences. The presequence translocase of the inner mitochondrial membrane (TIM23 complex) plays a central role in protein sorting. Preproteins are either translocated through the TIM23 complex into the matrix or are laterally released into the inner membrane. We report that the small hydrophobic protein Mgr2 controls the lateral release of preproteins. Mgr2 interacts with preproteins in transit through the TIM23 complex. Overexpression of Mgr2 delays preprotein release, whereas a lack of Mgr2 promotes preprotein sorting into the inner membrane. Preproteins with a defective inner membrane sorting signal are translocated into the matrix in wild-type mitochondria but are released into the inner membrane in Mgr2-deficient mitochondria. We conclude that Mgr2 functions as a lateral gatekeeper of the mitochondrial presequence translocase, providing quality control for the membrane sorting of preproteins. [Display omitted] •Mitochondrial preproteins en route through presequence translocase interact with Mgr2•Mgr2 delays the lateral release of preproteins into the mitochondrial inner membrane•Mgr2 prevents proteins with defective sorting signals from entering the inner membrane•This is a quality control system for the membrane sorting of mitochondrial preproteins The mitochondrial presequence translocase can transport preproteins to two different destinations, the inner membrane or matrix of mitochondria. Ieva et al. find that the small hydrophobic protein Mgr2 recognizes the sorting signal of preproteins and controls its release into the membrane, therefore providing quality control for the membrane sorting of proteins.