Premium
Zinc‐dependent intermembrane space proteins stimulate import of carrier proteins into plant mitochondria
Author(s) -
Lister Ryan,
Mowday Brett,
Whelan James,
Millar A. Harvey
Publication year - 2002
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.2002.01316.x
Subject(s) - intermembrane space , mitochondrion , mitochondrial intermembrane space , biochemistry , microbiology and biotechnology , valinomycin , zinc finger , biology , alternative oxidase , inner membrane , chemistry , membrane potential , bacterial outer membrane , escherichia coli , transcription factor , gene
Summary Mitochondrial inner membrane carrier proteins are imported into mitochondria from yeast, fungi and mammals by specific machinery, some components of which are distinct from those utilized by other proteins. Import of two different carriers into plant mitochondria showed that one contains a cleavable presequence which was processed during import, while the other imported in a valinomycin‐sensitive manner without processing. Mild osmotic shock of mitochondria released intermembrane space (IMS) components and impaired carrier protein import. Adding back the released IMS proteins as a concentrate in the presence of micromolar ZnCl 2 stimulated carrier import into IMS‐depleted mitochondria, but did not stimulate import of a non‐carrier control precursor protein, the alternative oxidase. Anion‐exchange separation of IMS components before addition to IMS‐depleted mitochondria revealed a correlation between several 9–10 kDa proteins and stimulation of carrier import. MS/MS sequencing of these proteins identified them as plant homologues of the yeast zinc‐finger carrier import components Tim9 and Tim10. Stimulation of import was dependent on either Zn 2+ or Cd 2+ and inhibited by both N‐ethylmalamide (NEM) and a divalent cation chelator, consistent with a functional requirement for a zinc finger protein. This represents direct functional evidence for a distinct carrier import pathway in plant mitochondria, and provides a tool for determining the potential function of other IMS proteins associated with protein import.