Nonself Recognition Through Intermolecular Disulfide Bond Formation of Ribonucleotide Reductase in Neurospora
Heterokaryon Incompatibility, Ribonucleotide Reductase, Nonself Recognition, Disulfide Bond
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-24PAincompatibility 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-24OR and UN-24PA. 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.
Smith, Robert P.; Kenji Wellman; Leila Haidari; Hirohisa Masuda; and Myron L. Smith. 2013. "Nonself Recognition Through Intermolecular Disulfide Bond Formation of Ribonucleotide Reductase in Neurospora." Genetics 193, (4): 1175-1183. http://nsuworks.nova.edu/cnso_bio_facarticles/7