Protein prenyltransferase alpha subunit - PFTA

Protein prenylation is the posttranslational attachment of either a farnesyl group or a geranylgeranyl group via a thioether linkage (-C-S-C-) to a cysteine at or near the carboxyl terminus of the protein. Farnesyl and geranylgeranyl groups are polyisoprenes, unsaturated hydrocarbons with a multiple of five carbons; the chain is 15 carbons long in the farnesyl moiety and 20 carbons long in the geranylgeranyl moiety. The alpha subunit is thought to participate in a stable complex with the isoprenyl substrate. In the alpha subunits of both types of protein prenyltransferases, seven tetratricopeptide repeats are formed by pairs of helices that are stabilised by conserved intercalating residues.