Prenyltransferases can attach either a farnesyl group or a geranylgeranyl group in thioether linkage to the cysteine residue of proteins with a C-terminal CAAX box. CAAX geranylgeranyltransferase and CAAX farnesyltransferase are heterodimers that share the same alpha subunit but have different beta subunits. This gene encodes the alpha subunit of these transferases. Alternative splicing results in multiple transcript variants. Related pseudogenes have been identified on chromosomes 11 and 13.