A novel motif at the C-terminus of palmitoyltransferases is essential for Swf1 and Pfa3 function in vivo

AYELEN GONZALEZ MONTORO; RODRIGO QUIROGA; HUGO J. F. MACCIONI; JAVIER VALDEZ TAUBAS

BIOCHEMICAL JOURNAL

PORTLAND PRESS LTD

Año: 2009 vol. 419 p. 301 - 308

0264-6021

S-acylation (commonly known as palmitoylation) is a widespreadpost-translational modification that consists of the addition ofa lipid molecule to cysteine residues of a protein through athioester bond. This modification is predominantly mediated bya family of proteins referred to as PATs (palmitoyltransferases).Most PATs are polytopic membrane proteins, with four to sixtransmembrane domains, a conserved DHHC motif and variableC-and N-terminal regions, that are probably responsible forconferring localization and substrate specificity. There is verylittle additional information on the structure–function relationshipof PATs. Swf1 and Pfa3 are yeastmembers of theDHHCfamily ofproteins. Swf1 is responsible for the S-acylation of severaltransmembrane SNAREs (soluble N-ethylmaleimide-sensitivefusion protein-attachment protein receptors) and other integralmembrane proteins. Pfa3 is required for the palmitoylation ofVac8, a protein involved in vacuolar fusion. In the presentstudy we describe a novel 16-amino-acid motif present at thecytosolic C-terminus of PATs, that is required for Swf1 and Pfa3function in vivo. Within this motif, we have identified a singleresidue in Swf1, Tyr323, as essential for function, and this is correlatedwith lack of palmitoylation of Tlg1, a SNARE that is asubstrate of Swf1. The equivalent mutation in Pfa3 also affectsits function. These mutations are the first phenotype-affectingmutations uncovered that do not lie within the DHHC domain,for these or any other PATs. The motif is conserved in 70%of PATs from all eukaryotic organisms analysed, and may haveonce been present in all PATs. We have named this motif PaCCT(‘Palmitoyltransferase Conserved C-Terminus’).