title: Nonself recognition through intermolecular disulfide bond formation of ribonucleotide reductase in neurospora.
abstract: Type I ribonucleotide reductases (RNRs) are conserved across diverse taxa and are essential for the conversion of RNA into DNA precursors. In Neurospora crassa, the large subunit of RNR (UN-24) is unusual in that it also has a nonself recognition function, whereby coexpression of Oak Ridge (OR) and Panama (PA) alleles of un-24 in the same cell leads to growth inhibition and cell death. We show that coexpressing these incompatible alleles of un-24 in N. crassa results in a high molecular weight UN-24 protein complex. A 63-amino-acid portion of the C terminus was sufficient for un-24(PA) incompatibility activity. Redox active cysteines that are conserved in type I RNRs and essential for their catalytic function were found to be required for incompatibility activity of both UN-24(OR) and UN-24(PA). Our results suggest a plausible model of un-24 incompatibility activity in which the formation of a complex between the incompatible RNR proteins is potentiated by intermolecular disulfide bond formation.
authors: Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada. rsmith@nova.edu
authors: Robert P
authors: RP
authors: Smith
authors: Kenji
authors: K
authors: Wellman
authors: Leila
authors: L
authors: Haidari
authors: Hirohisa
authors: H
authors: Masuda
authors: Myron L
authors: ML
authors: Smith
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D020134:Catalytic Domain; D049109:Cell Proliferation; D003545:Cysteine / Q000737:chemistry / Q000235:genetics; D004220:Disulfides / Q000737:chemistry*; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009492:Neurospora crassa / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D055503:Protein Multimerization; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012264:Ribonucleotide Reductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D004220:Disulfides; D005656:Fungal Proteins; D021122:Protein Subunits; D012264:Ribonucleotide Reductases; D003545:Cysteine