CYLD_phos_site is a natively unstructured region on a subset of tumour-suppressor and de-ubiquitinating enzyme CYLD proteins in eukaryotes. It lies between the second pair of CAP_GLY domains, Pfam:PF01302, on these proteins. This region of CYLD, being unstructured, carries a number of serine residues which, in response to cellular stimuli, become phosphorylated. This transient phosphorylation-state induces ubiquitination of TRAF2, a ubiquitin ligase that catalyses both self-ubiquitination and the ubiquitination of specific target molecules involved in signal transduction [1].

1: Regulation of the deubiquitinating enzyme CYLD by IkappaB kinase gamma-dependent phosphorylation. Reiley W, Zhang M, Wu X, Granger E, Sun SC; Mol Cell Biol. 2005;25:3886-3895. PMID:15870263