Functional analysis of the hemK gene product involvement in protoporphyrinogen oxidase activity in yeast

The Escherichia coil hemK gene has been described as being involved in prot oporphyrinogen oxidase activity; however, there is no biochemical evidence for this. In the context of characterizing the mechanisms of protoporphyrin ogen oxidation in the yeast Saccharomyces cerevisiae, we investigated the y east homolog of HemK, which is encoded by the ORF YNL063w, to find out whet her it has any protoporphyrinogen oxidase activity and/or whether it modula tes protoporphyrinogen oxidase activity. Phenotype analysis and enzyme acti vity measurements indicated that the yeast HemK homolog is not involved in protoporphyrinogen oxidase activity. Complementation assays in which the ye ast HemK homolog is overproduced do not restore wild-type phenotypes in a y east strain with deficient protoporphyrinogen oxidase activity. Protein seq uence analysis of HemK-related proteins revealed consensus motif for S-aden osyl-methionine-dependent methyltransferase. (C) 1999 Federation of Europea n Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.