8.A.114.1.5
The ZDHHC9-GOLGA7 complex is a palmitoyltransferase specific for hRAS and nRAS (Swarthout et al. 2005). DHHC (Asp-His-His-Cys) palmitoyltransferases are eukaryotic integral membrane enzymes that catalyze protein palmitoylation, which is important in a range of physiological processes, including small guanosine triphosphatase (GTPase) signaling, cell adhesion, and neuronal receptor scaffolding.  Rana et al. 2018 presented crystal structures of two DHHC palmitoyltransferases and a covalent intermediate mimic. The active site resides at the membrane-cytosol interface allow the enzyme to catalyze thioester-exchange using fatty acyl-coenzyme A, explaining why membrane-proximal cysteines are candidates for palmitoylation. The acyl chain binds in a cavity formed by the transmembrane domain. Rana et al. 2018 proposed a mechanism for acyl chain-length selectivity in DHHC enzymes on the basis of cavity mutants with preferences for shorter and longer acyl chains. Protein S-acylation is a reversible lipidic posttranslational modification where a fatty acid chain is covalently linked to cysteine residues by a thioester linkage (Rana et al. 2018).