Adhesin involved in diffuse adherence (AIDA-I) belongs to the group of monomeric autotransporters (AT) and is an important virulence factor that mediates auto-aggregation, biofilm formation, adhesion and invasion into host cells [, , , ]. The AIDA repeat is found on bacterial autotransporter proteins. As the repeat is short and occurs multiple times, it is likely to be the region of the transporter that acts as the stalk between the β-barrel inserted into the membrane and the N-terminal head domain.
This entry represents the N-terminal domain of the axin interactor, dorsalization-associated protein family AIDA []. AIDA acts as a ventralizing factor during embryogenesis. It inhibits axin-mediated JNK activation by binding axin and disrupting axin homodimerization. This in turn antagonizes a Wnt/beta-catenin-independent dorsalization pathway activated by axin/JNK-signaling [].
This entry represents the N-terminal domain of the axin interactor, dorsalization-associated protein (AIDA) superfamily []. AIDA acts as a ventralizing factor during embryogenesis. It inhibits axin-mediated JNK activation by binding axin and disrupting axin homodimerization. This in turn antagonizes a Wnt/beta-catenin-independent dorsalization pathway activated by axin/JNK-signaling []. The core structure of the AIDA N-terminal domain consists of four helices arranged in a close or partly open bundle fold with left-handed twist going up-and-down.
Both Aah (autotransporter adhesin heptosyltransferase) and TibC are protein O-heptosyltransferases that act on multiple sites from repeat regions of proteins exported by autotransporters. Aah glycosylates AIDA (autotransporter adhesin involved in diffuse adherence) and TibC acts on TibA (enterotoxigenic invasion locus B). TibC is able to replace Aah, suggesting that both represent a novel class of heptosyltransferases specifically transferring heptose residues onto multiple sites of a protein backbone [, ].
The axin interaction dorsalization-associated (Aida) protein was characterised in zebrafish as a protein that utilizes its C-terminal region to interact with axis formation inhibitor (Axin), which is a microtubule-interacting scaffold protein for several distinct signalling proteins in the Wnt cascade. The C-terminal region of the Aida protein is a distinct version of the C2 domain. This Aida-type C2 domain is found in the C-terminal region of the proteins and it is critical for interactions with cytoskeletal in the context of cellular adhesion points, thus, it is combined with diverse domains related to cytoskeletal functions, e.g. EF hands, coiled coils, IQ calmodulin-binding motifs, ankyrin repeats and myosin head motor domain, or with a second lipid-binding domain, e.g. the PH domain. The Aida-type C2 domain is found only in the metazoan, choanoflagellate, chromist and chlorophyte lineages [, ].This domain has predominantly a β-strand globular fold composed of an antiparallel β-sandwich with two β-sheets, and three short α-helices to stabilize the conformation [].
