The Saccharomyces cerevisiae mevalonate diphosphate decarboxylase (Erg19p)forms homodimers in vivo, and a single substitution in a structurally conserved region impairs dimerization

The wild-type ERG19 gene of the yeast Saccharomyces cerevisiae encoding mev alonate diphosphate decarboxylase (MVD) and the mutated recessive erg19-34 allele leading to a decrease of sterol production and to a thermosensitive phenotype have been characterized [2]. The mutated erg19-34 allele bears a single amino acid leucine79-to-proline (L79P) substitution. It was shown th at this mutation does not affect the level of production of the enzyme. We performed a two-hybrid assay to show that the yeast Saccharomyces cerevisia e MVD forms homodimers in vivo and that the single point mutation drastical ly impairs the oligomerization of the protein, thereby explaining the defic iency of MVD activity observed in the temperature-sensitive strain.