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Peripheral mitochondrial inner membrane protein, Mss2p, required for export of the mitochondrially coded Cox2p C tail

S A Broadley1, C M Demlow, T D Fox

  • 1Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA.

Molecular and Cellular Biology
|October 18, 2001
PubMed

Insights

Mss2p is crucial for cytochrome oxidase subunit 2 (Cox2p) accumulation in yeast mitochondria, not synthesis. It facilitates Cox2p C-terminal export, essential for cytochrome oxidase assembly.

Area of Science:

  • Mitochondrial biology
  • Protein transport
  • Molecular genetics

Background:

  • Cytochrome oxidase subunit 2 (Cox2p) biogenesis involves matrix-side synthesis and inner membrane export.
  • The Saccharomyces cerevisiae gene MSS2 is known to be essential for Cox2p accumulation.

Purpose of the Study:

  • To elucidate the precise role of Mss2p in Cox2p biogenesis.
  • To determine if Mss2p is involved in Cox2p synthesis or post-synthesis processing and export.

Main Methods:

  • Pulse-labeling studies to assess Cox2p synthesis rates.
  • Expression of ARG8(m) reporter in COX2 locus of mss2 mutants.
  • Analysis of Cox2p stability and assembly in wild-type and mutant strains.
  • Investigating the effect of Yta10p (Afg3p) protease inactivation on Cox2p.

Main Results:

  • Mss2p is required for Cox2p accumulation, not its synthesis.
  • In mss2 mutants, Cox2p C-terminal export and subsequent assembly into cytochrome oxidase are blocked.
  • Partial stabilization of Cox2p occurs in mss2 mutants with inactivated Yta10p (Afg3p) AAA-protease, but assembly is not restored.
  • Mss2p is peripherally associated with the inner mitochondrial membrane.

Conclusions:

  • Mss2p functions in recognizing and promoting the export of the Cox2p C-terminal tail from the mitochondrial matrix.
  • Mss2p is essential for the proper assembly of cytochrome oxidase by facilitating Cox2p C-terminal export.

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