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Hernandez-Saavedra NY: Cu,Zn superoxide dismutase in Rhodotorula and Udeniomyces spp. isolated from sea water: cloning and sequencing the encoding region. Yeast. 2003 Apr 30;20(6):479-92.
The gene encoding the copper-zinc superoxide dismutase enzyme (SODC or Cu,Zn-SOD) has been cloned from several species of higher eukaryotes, but superoxide dismutase genes from moulds and yeast have not been studied extensively. Only 15 nucleotide sequences have been reported in the SwissProt, EMBL and GenBank data libraries. In general the presence of Cu,Zn-SOD in cytosol, as well as Mn-SOD in the mitochondrial matrix of yeast, has been accepted. The absence of Cu,Zn-SOD in a pigmented yeast has been accepted as a general rule. Some authors suggest that the absence of Cu,Zn-SOD in pigmented yeast is complemented by the presence of carotenoproteins that act as an extra mitochondrial antioxidant. In this report, we found that the absence of SODC is not a rule for pigmented yeast: Udeniomyces puniceus expresses an active SODC which responds to Cu (2+) induction, as has been reported previously for non-pigmented yeast. The encoding region of the sod1 gene was cloned from three species of pigmented marine yeast thorough genomic DNA PCR amplification. Fragments of 485-487 nucleotides were obtained, which contain information for theoretical products of 153-154 amino acids. In Rhodotorula mucilaginosa the deduced amino acid sequence shows that insertion of three bases (C (112), A (149) and C (166)) generates a stop codon at position 123 (TGA). For Rhodotorula graminis a single change (T for A) generates a stop codon at position 298. For both species, this non-transcription of encoding sequence correlates with the absence of peptides or active proteins in cell homogenates. For U. puniceus, the cloned nucleotide sequence contains all necessary information to produce a functional protein, which correlates with activity detected in cell homogenates, both under normal conditions and by copper induction experiments. Finally, we clearly showed that the key factor in protection against oxidative stress on pigmented yeast is related not only to the presence of protective pigments but also to their amounts and spectra, as well as the presence and activity of SODC. |
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