The residues upstream of this domain are the probable palmitoylation sites, particularly two cysteines. The domain has a putative PEST site at the very start that seems to be responsible for poly-ubiquitination [1]. PEST domains are polypeptide sequences enriched in proline (P), glutamic acid (E), serine (S) and threonine (T) that target proteins for rapid destruction. The whole domain, in conjunction with a C-terminal domain of the longer protein, is necessary for dimerisation of the whole protein [2].

1: PEST sequences and regulation by proteolysis. Rechsteiner M, Rogers SW; Trends Biochem Sci. 1996;21:267-271. PMID:8755249

2: Molecular dissociation of the role of PSD-95 in regulating synaptic strength and LTD. Xu W, Schluter OM, Steiner P, Czervionke BL, Sabatini B, Malenka RC; Neuron. 2008;57:248-262. PMID:18215622