A NOVEL MOTIF AT THE C-TERMINUS OF PALMITOYLTRANSFERASES IS ESSENTIAL FOR SWF1 FUNCTION IN VIVO

GONZÁLEZ MONTORO, AYELÉN; QUIROGA, RODRIGO; VALDEZ TAUBAS, JAVIER

Carlos Paz, Córdoba, Argentina.

Congreso; XLIV Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2008

SAIB

S-acylation (also known as palmitoylation) is the addition of a lipidmolecule to cysteine residues of a protein through a thioester bond.This modification is mediated by proteins referred to asPalmitoyltransferases (PATs), characterised by the presence of aconserved DHHC-Cysteine-Rich Domain. Swf1 is a yeast memberof the DHHC family, and it is responsible for the S-acylation ofseveral SNARES and other membrane proteins. Here we describe anovel 16 amino acid motif, present at the cytosolic C-terminus ofPATs, that is required for Swf1 function in vivo. Within this motif,we have identified a single residue in Swf1, Tyr-323, as essential forfunction, and this is correlated with lack of palmitoylation of Tlg1, aSNARE that is a substrate of Swf1. Substitution of Tyr-323 withAlanine is the first phenotype affecting mutation uncovered thatdoes not lie within the DHHC domain, for this or any other PAT. Insilico analyses indicate that the motif is conserved in 70% of allPATs, and suggest that the motif may have once been present in allPATs. We named this motif ?Palmitoyltransferase Conserved C- Terminus? (PaCCT). Additionally, while searching for a funtion for  the PaCCT domain, we obtained preliminary evidence indicating that the Cytosolic C-terminus of Swf1 interacts with palmitoyl-CoA, the lipid donor in S-acylaction, albeit independently of thePaCCT domain.