Deletion of the carbonic anhydrase-like gene NCE103 of the yeast Saccharomyces cerevisiae causes an oxygen-sensitive growth defect

The yeast protein Nce103p encoded by the gene NCE103 (YNL036w) was describe d by Cleves et al. (1996) as a substrate of the non-classical export pathwa y which acts independently of the classical pathway through the ER and the Golgi compartments. However, the predicted amino acid sequence of Nce103p s hows high levels of identities to carbonic anhydrases of pro- and eukaryote s. A nce103-Delta deletion strain did not grow on a rich peptone-yeast extr act-glucose medium under normal aerobic conditions at pH values of 3.0-8.0, but grew like wild-type in an oxygen-free nitrogen or oxygen-reduced atmos phere over this pH range, and was more sensitive to H2O2 than wild-type. No carbonic anhydrase activity could be detected in crude extracts prepared f rom wild-type, nce103-Delta mutants or in strains transformed with a multic opy plasmid carrying the NCE103 gene. Expression of the Medicago saliva car bonic anhydrase gene (Coba de la Pena et al., 1997), in a yeast expression cassette on a multicopy plasmid, complemented the growth defects caused by the nce103-Delta deletion and carbonic anhydrase activity could be readily detected in the crude extract. The ability of the nce103-Delta deletion str ain to grow like wild-type under anaerobic conditions suggests that the pro tein encoded by NCE103 is required for protection against certain products of an oxidative metabolism and can be replaced in this function by the Medi cago sativa carbonic anhydrase, A NCE103 promoter-LacZ fusion in a wild-typ e background showed that NCE103 is poorly transcribed under aerobic conditi ons and at an undetectable level under anaerobic conditions. Copyright (C) 1999 John Wiley & Sons, Ltd.