T. Hunter et al., CLONING, EXPRESSION, AND CHARACTERIZATION OF 2 MANGANESE SUPEROXIDE DISMUTASES FROM CAENORHABDITIS-ELEGANS, The Journal of biological chemistry, 272(45), 1997, pp. 28652-28659
Two genes encoding manganese superoxide dismutase (sod-2 and sod-3) ha
ve been identified in the nematode Caenorhabditis elegans. Each gene i
s composed of five exons, and intron positions are identical; however,
intron sizes and sequences are not the same, The predicted protein se
quences are 86.3% homologous (91.8% conservative), and the cDNAs are o
nly 75.2% homologous, Both deduced protein sequences contain the expec
ted N-terminal mitochondrial transit peptides. Reverse transcriptase p
olymerase chain reaction analysis shows that both genes are expressed
under normal growth conditions and that their RNA transcripts are tran
s-spliced to the SL-1 leader sequence. The latter result together with
Northern blot analysis indicate that both genes have mono-cistronic t
ranscripts, The sod-3 gene was mapped to chromosome X, and the locatio
n of sod-2 was confirmed to be chromosome I, Polymerase chain reaction
was used to amplify the cDNA regions encoding the predicted mature ma
nganese superoxide dismutase proteins and each was cloned and expresse
d to high levels in Escherichia coli cells deficient in cytosolic supe
roxide dismutases. Both proteins were shown to be active in E. coli, p
roviding similar protection against methyl viologen-induced oxidative
stress. The expressed enzymes, which were not inhibited by hydrogen pe
roxide or cyanide, are dimeric, show quite different electrophoretic m
obilities and isoelectric points, but exhibit comparable specific acti
vities.