Structural and Functional Requirements for Activity of the Tim9-Tim10 Complex in Mitochondrial Protein Import
Details
Publication Year 2009-02, Volume 20, Issue #3, Page 769-779
Journal Title
MOLECULAR BIOLOGY OF THE CELL
Publication Type
Journal Article
Abstract
The Tim9-Tim10 complex plays an essential role in mitochondrial protein import by chaperoning select hydrophobic precursor proteins across the intermembrane space. How the complex interacts with precursors is not clear, although it has been proposed that Tim10 acts in substrate recognition, whereas Tim9 acts in complex stabilization. In this study, we report the structure of the yeast Tim9-Tim10 hexameric assembly determined to 2.5 angstrom and have performed mutational analysis in yeast to evaluate the specific roles of Tim9 and Tim10. Like the human counterparts, each Tim9 and Tim10 subunit contains a central loop flanked by disulfide bonds that separate two extended N- and C-terminal tentacle-like helices. Buried salt-bridges between highly conserved lysine and glutamate residues connect alternating subunits. Mutation of these residues destabilizes the complex, causes defective import of precursor substrates, and results in yeast growth defects. Truncation analysis revealed that in the absence of the N- terminal region of Tim9, the hexameric complex is no longer able to efficiently trap incoming substrates even though contacts with Tim10 are still made. We conclude that Tim9 plays an important functional role that includes facilitating the initial steps in translocating precursor substrates into the intermembrane space.
Publisher
AMER SOC CELL BIOLOGY
Keywords
SMALL TIM PROTEINS; INTERMEMBRANE SPACE; ADP/ATP CARRIER; OUTER-MEMBRANE; PRECURSOR PROTEINS; CYTOCHROME-C; TRANSLOCATION; PATHWAY; SYSTEM; RECRUITMENT
Rights Notice
Refer to copyright notice on published article.


Creation Date: 2009-02-01 12:00:00
Last Modified: 0001-01-01 12:00:00
An error has occurred. This application may no longer respond until reloaded. Reload 🗙