Terminal protein association and sequence homology in linear mitochondrial plasmid-like DNAs of sorghum and maize

The linear extrachromosomal mitochondrial plasmid-like DNAs from the Ru cytoplasm of maize, and M35-1 and IS1112C cytoplasms of sorghum, possess 5 terminally-attached proteins. These molecules required proteinase K treatment for mobility in agarose gels and were susceptible to exonuclease III but not lambda exonuclease cleavage. Hybridizations, under stringent conditions, indicated that the sorghum plasmid-like DNAs, N1 and N2, did not possess DNA sequence homology to cloned central regions of S1 and S2, the linear mitochondrial plasmid-like DNAs present in S cytoplasm of maize. In addition, a novel 4.2kb, DNAase sensitive, RNAase insensitive band, exhibiting homology to internal sequences from maize S2, was observed in the sorghum IS1112C cytoplasm only.