The Intrinsically Disordered Termini of zDHHC S-Palmitoyltransferases Facilitate Multiple Regulatory Functions

Abstract

zDHHC protein acyltransferases (PATs) are a family of membrane proteins that catalyze the reversible post-translational lipidation known as palmitoylation, a process essential to normal cellular function through facilitation of membrane attachment, subcellular trafficking, and protein stability. While transmembrane proteins such as PATs are mostly ordered due to the hydrophobic membrane environment, they have cytoplasmic tails which tend to lack stable three-dimensional structure. The aim of this study was to understand the structural and functional implications of disordered PAT termini using computational, biochemical, and biophysical approaches. Intrinsic disorder prediction indicates that a conserved α-helical molecular recognition feature (MoRF) exists in the C-termini of all PATs. In the human and yeast Ras PATs (zDHHC9 and Erf2, respectively), this region was found to be essential to palmitoyltransferase function in vivo and in vitro. Additional experiments suggest that the MoRF participates in previously undescribed protein-protein interactions. The disordered termini of Erf2 also facilitate multiple regulatory post-translational modifications including phosphorylation, acetylation, and ubiquitination. As PTMs and protein-protein interactions of PATs have been poorly described, elucidation of the structure-function relationships and modifications of intrinsically disordered regions in PATs potentially represents a novel paradigm of pharmacological interrogation of protein palmitoylation.