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

AYELEN GONZALEZ MONTORO; RODRIGO QUIROGA; JAVIER VALDEZ TAUBAS

CARLOS PAZ, PROV. DE CÓRDOBA, REP. ARGENTINA

Congreso; XLIV Reunión Anual -SAIB; 2008

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

A NOVEL MOTIF AT THE C-TERMINUS OF PALMITOYLTRANSFERASES IS ESSENTIAL FOR SWF1 FUNCTION IN VIVO Ayelén GONZÁLEZ MONTORO, Rodrigo QUIROGA, y Javier VALDEZ TAUBAS S-acylation (also known as palmitoylation) is the addition of a lipid molecule to cysteine residues of a protein through a thioester bond. This modification is mediated by proteins referred to as Palmitoyltransferases (PATs), characterised by the presence of a conserved DHHC-Cysteine-Rich Domain. Swf1 is a yeast member of the DHHC family, and it is responsible for the S-acylation of several SNARES and other membrane proteins. Here we describe a novel 16 amino acid motif, present at the cytosolic C-terminus of PATs, that is required for Swf1 function in vivo. Within this motif, we have identified a single residue in Swf1, Tyr-323, as essential for function, and this is correlated with lack of palmitoylation of Tlg1, a SNARE that is a substrate of Swf1. Substitution of Tyr-323 with Alanine is the first phenotype affecting mutation uncovered that does not lie within the DHHC domain, for this or any other PAT. In silico analyses indicate that the motif is conserved in 70% of all PATs, and suggest that the motif may have once been present in all PATs. We named this motif ?Palmitoyltransferase Conserved C-Terminus? (PaCCT). Additionally, while searching for a PaCCT domain function, we have obtained preliminary evidence that indicates that the Cytosolic C-terminus of Swf1 interacts with palmitoyl-CoA, the lipid donor in S-acylaction, albeit independently of the PaCCT domain.