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

Journal Article (Review;Journal Article)

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.

Full Text

Duke Authors

Cited Authors

  • Rhoads, DM; Levings, CS; Siedow, JN

Published Date

  • August 1995

Published In

Volume / Issue

  • 27 / 4

Start / End Page

  • 437 - 445

PubMed ID

  • 8595979

Electronic International Standard Serial Number (EISSN)

  • 1573-6881

International Standard Serial Number (ISSN)

  • 0145-479X

Digital Object Identifier (DOI)

  • 10.1007/bf02110006


  • eng