Isolation and characterization of a cDNA for mitochondrial manganese superoxide dismutase (SOD-3) of maize and its relation to other manganese superoxide dismutases.

We describe the isolation of a cDNA clone for the nuclear-encoded manganese superoxide dismutase (SOD-3) of maize mitochondria. The cDNA, pSod3.1c, selects by hybridization an RNA which produces the SOD-3 precursor upon in vitro translation. The DNA sequence of pSod3.1c was determined from fragments subcloned in M13. The amino-acid sequence deduced from the nucleotide sequence displays significant homology with the amino-acid sequences of prokaryotic and eukaryotic Mn-SODs, but displays greater homology with mammalian Mn-SOD than it does with yeast or bacterial Mn-SOD. A 31 amino-acid transit peptide also is encoded by the pSod3.1c clone. Analysis of poly(A)+ RNA indicates that Sod3 mRNA is approx. 1250 nucleotides in length. The amount of Sod3 transcript in seedling leaves is increased by light.