Reference "Two cDNAs encode two nearly identical Cu/Zn superoxide dismutase proteins in maize"

Reference ID

7361

Title

Two cDNAs encode two nearly identical Cu/Zn superoxide dismutase proteins in maize

Source

Molecular & General Genetics, 1989, vol. 219, pp. 1-8

Authors (2)

Cannon-R-E

Scandalios-J-G

Abstract

SOD-4, a cytosolic form of superoxide dismutase in maize, originally was defined
as a single band of activity by zymogram analysis. The protein was purified to
"homogeneity" as shown by a single band on native or denaturing polyacrylamide
gels and a single spot on two dimensional gels. The N-terminal amino acid
sequence for the first 20 residues was determined for the purified SOD-4
protein. All residues were clearly determined except for residue twelve, where
both glutamic and aspartic acids were found. A maize lambda gt11 cDNA library
was constructed from scutellar poly(A)+ RNA. Two cDNAs were isolated,
restriction mapped, and their DNA sequences determined. The amino acid sequence
deduced from both cDNAs matched perfectly the N-terminal sequence of the
purified protein except for the residue at position 12. Significantly, at the
twelfth codon, one cDNA was found to code for glutamic acid and the other cDNA
had a codon for aspartic acid. Both cDNAs contained similar but not identical 5'
and 3' untranslated sequences. Both cDNAs contained polyadenylation signals and
tails. cDNA isolations, RNA, and genomic DNA blots confirm the existence and
expression of two genes that produce indistinguishable SOD-4 proteins.