Tight junction protein ZO-3 (IPR005420)

Short name: ZO-3

Overlapping homologous superfamilies


Family relationships


The zona occuldens proteins (ZO-1, ZO-2 and ZO-3) are a family of tight junction associated proteins that function as cross-linkers, anchoring the TJ strand proteins to the actin-based cytoskeleton [PMID: 9214391]. Each protein contains three PDZ (postsynaptic density, disc-large, ZO-1) domains, a single SH3 (Src Homology-3) domain and a GK (guanylate kinase) domain, the presence of which identifies them as members of the membrane-associated guanylate kinase (MAGUK) protein family. They also share an acidic domain at the C-terminal region of the molecules not found in other MAGUK proteins. It has been demonstrated that the first PDZ domain is involved in binding the C-terminal -Y-V motif of claudins [PMID: 10601346]. By contrast, the occludin-binding domain of ZO-1 has been shown to lie in the GK and acidic domains [PMID: 9792688]. Although the precise location of the actin-binding motif has not been elucidated, it appears to be within the C-terminal half of the molecules, since transfection of this region into fibroblasts induces co-localisation of ZO-1 and ZO-2 with actin fibres.

This entry represents ZO-3, which was first identified as a 130kDa protein that co-immunoprecipitates with ZO-1 [PMID: 8408213]. It shares ~65% overall similarity with ZO-1 and ZO-2 proteins, with highest levels of similarity in the MAGUK and acid domains. In vitro binding studies indicate that ZO-3 may interact directly with ZO-1 through its second PDZ domain, although it does not appear to bind directly to ZO-2 [PMID: 9531559].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

No terms assigned in this category.

Cellular Component

GO:0005923 bicellular tight junction

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.