PROSITE documentation PDOC00699

Ependymins signatures

Ependymins were originally identified in the ependymal zone of goldfish brain and are the major glycoprotein component of cerebrospinal fluid (CSF) in various orders of teleost fish [1,2,3,4]. Several N-glycosylation variants of ependymin have been identified and an important role appears to be the binding of calcium via N-linked sialic acid residues [5]. The precise function of ependymins is still being elucidated. Beside the piscine ependymin this group is formed by Ependymin Related Proteins (ERP) in Xenopus and in mammals (MERP or UCC1).

A predominant feature of MERPs, Xenopus ERP and fish ependymins is the four conserved cysteine residues. Potentially, these cysteine residues may be important in maintaining protein conformation through disulfide bonding. Human and mouse MERPs are of similar length to fish ependymins (224 amino acids) and, like fish ependymins, are predominantly hydrophilic and contain a cleavable hydrophobic signal sequence that is typical of secretory proteins [6].

We developed two signature patterns for ependymins. The first one corresponds to a well conserved region located between two conserved N-glycosylation sites and which include a conserved cysteine residue. The second pattern is located in the C-terminal section and also includes one of the conserved cysteines.