URF13, a ligand-gated, pore-forming receptor for T-toxin in the inner membrane of cms-T mitochondria

J Bioenerg Biomembr. 1995 Aug;27(4):437-45. doi: 10.1007/BF02110006.

Abstract

URF13 is the product of a mitochondrial-encoded gene (T-urf13) found only in maize plants containing the Texas male-sterile cytoplasm (cms-T), and it is thought to be responsible for both cytoplasmic male sterility and the susceptibility of cms-T maize to the fungal pathogens Bipolaris maydis race T and Phyllosticata maydis. Mitochondria isolated from cms-T maize are uniquely sensitive to pathotoxins (T-toxin) produced by these fungi and to methomyl (a commercial insecticide). URF13 acts as a receptor that specifically binds T-toxin to produce hydrophilic pores in the inner mitochondrial membrane. When expressed in Escherichia coli cells, URF13 also forms hydrophilic pores in the plasma membrane if exposed to T-toxin or methomyl. Topological studies established that URF13 contains three membrane-spanning alpha-helices, two of which are amphipathic and can contribute to pore formation. Chemical cross-linking of URF13 was used to demonstrate the existence of URF13 oligomers in cms-T mitochondria and E. coli cells. The ability of the carboxylate-specific reagent, N,N'-dicyclohexycarbodiimide, to cross-link URF13 was used in conjunction with site-directed mutagenesis to establish that the URF13 tetramer has a central core consisting of a four-alpha-helical bundle which undergoes a conformational change after interaction with T-toxin or methomyl. Overall, the experimental evidence indicates that URF13 functions as a ligand-gated, pore-forming T-toxin receptor in cms-T mitochondria.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Review

MeSH terms

  • Amino Acid Sequence
  • DNA, Mitochondrial / metabolism
  • Genes, Plant*
  • Intracellular Membranes / metabolism
  • Intracellular Membranes / ultrastructure
  • Mitochondria / metabolism*
  • Mitochondria / ultrastructure
  • Mitochondrial Proteins*
  • Models, Structural
  • Molecular Sequence Data
  • Mycotoxins / metabolism*
  • Plant Diseases
  • Plant Leaves
  • Plant Proteins / chemistry
  • Plant Proteins / genetics
  • Plant Proteins / metabolism*
  • Protein Structure, Secondary
  • Reproduction
  • Zea mays / metabolism*

Substances

  • DNA, Mitochondrial
  • Mitochondrial Proteins
  • Mycotoxins
  • Plant Proteins
  • URF13 protein, Zea mays