Immunochemical and Mutational Analyses of P-type ATPase Spf1p Involved in the Yeast Secretory Pathway(Biochemistry & Molecular Biology)

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The yeast SPF1 gene encodes a novel P-type ATPase, the substrate of which specificity has not been identified. It is required for sensitivity to SMKT, a killer toxin produced by the halotolerant yeast Pichia farinosa. To investigate the function of Spflp, Asp487, the putative phosphorylation site of Spflp, was replaced by Asn. Expression of the altered SPF1, with Asp487 replaced by Asn, did not suppress the SMKT-resistant phenotype of spfl mutants, suggesting that the catalytic activity of this ATPase is required for acquisition of sensitivity to SMKT. Subcellular fractionation experiments indicated that the fractionation pattern of Spflp was similar to that of an early Golgi protein, Ochlp. Cells lacking Spflp had an abnormal fractionation pattern of Secl2p. The spf1 disruptant also showed increased expression of Kar2p and sensitivity to tunicamycin. The glycosylation-defective phenotype and possible role of Spflp in the secretory pathway are discussed.
2001-11-23