Biochemical and functional characterization of ORF138, a mitochondrial protein responsible for Ogura cytoplasmic male sterility in Brassiceae

Biochimie. 2005 Dec;87(12):1089-100. doi: 10.1016/j.biochi.2005.05.009. Epub 2005 Jun 9.

Abstract

In cytoplasmic male sterility (CMS), original mitochondrial genes contribute to sex determinism by provoking pollen abortion. The function of the encoded proteins remains unclear. We studied the ORF138 protein, responsible for the 'Ogura' CMS, which is both used in hybrid seed production and present in natural populations. We analyzed the biochemical and structural properties of this protein in male-sterile plants and in E. coli. We showed that this protein spontaneously forms dimers in vitro. Truncated variants of the protein, containing either the hydrophobic or the hydrophilic moiety, also spontaneously dimerize. By fractionating mitochondria, we showed that ORF138 was strongly associated with the inner mitochondrial membrane of male-sterile plants. Our results also strongly suggest that ORF138 forms oligomers in male-sterile plant mitochondria. In E. coli, ORF138 was associated with the plasma membrane, as shown by membrane fractionation, and formed oligomers. The production of this protein strongly inhibited bacterial growth, but not by inhibiting respiration. The observed toxic effects required both the hydrophilic and hydrophobic moieties of the protein.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Brassica / metabolism*
  • DNA Primers
  • Escherichia coli / genetics
  • Escherichia coli / growth & development
  • Kinetics
  • Mitochondria / metabolism*
  • Mitochondrial Proteins / chemistry*
  • Mitochondrial Proteins / genetics
  • Mitochondrial Proteins / metabolism*
  • Plant Infertility*
  • Plant Proteins / chemistry*
  • Plant Proteins / genetics
  • Plant Proteins / metabolism*
  • Plasmids
  • Reproduction
  • Restriction Mapping

Substances

  • DNA Primers
  • Mitochondrial Proteins
  • Plant Proteins