Serine-threonine protein kinase activity of Elm1p, a regulator of morphologic differentiation in Saccharomyces cerevisiae.

The Saccharomyces cerevisiae gene ELM1 regulates morphologic differentiation and its nucleotide sequence predicts a novel protein kinase. Elm1p was expressed in yeast and insect cells and purified. Elm1p displayed protein kinase activity in autophosphorylation assays and towards exogenous substrates. Serine and threonine residues were identified as the acceptors in these reactions. These data together with previous genetic analysis of ELM1 function indicate that phosphorylation on serine and/or threonine residues of a particular substrate or set of substrates by Elm1p is required for repression of the filamentous growth differentiation state.