Camguk, Lin-2, and CASK: novel membrane-associated guanylate kinase homologs that also contain CaM kinase domains.

MAGUKs (membrane-associated guanylate kinase homologs) are proteins involved in cell junction organization, tumor suppression, and signalling. Their structure includes one or three copies of a DHR or PDZ domain (discs-large homologous region or PSD-95/SAP90, discs-large ZO-1 homologous domain), an SH3 domain, and a guanylate kinase domain. MAGUKs were classified into two subfamilies: Dlg-like with three DHR/PDZ domains and p55-like with a single DHR/PDZ domain. There is now a new subfamily whose members have a novel domain structure: a calcium/calmodulin-dependent protein kinase domain in the N-terminus as well as the DHR/PDZ, SH3 and GUK domains in the C-terminus. These new MAGUKs may regulate transmembrane molecules that bind calcium, calmodulin, or nucleotides, camguk (cmg) is a Drosophila member of this novel MAGUK subfamily; we report its sequence and domain structure.