CHDL: a cadherin-like domain in Proteobacteria and Cyanobacteria.

We identified a cadherin-like domain (CHDL) using computational analysis. The CHDL domain is mostly distributed in Proteobacteria and Cyanobacteria, although it is also found in some eukaryotic proteins. Prediction of three-dimensional protein folding indicated that the CHDL domain has an immunoglobulin beta-sandwich fold and belongs to the cadherin superfamily. The CHDL domain does not have LDRE and DxNDN motifs, which are conserved in the cadherin domain, but has three other motifs: PxAxxD, DxDxD and YT-V/I-S/T-D, which might contribute to forming a calcium-binding site. The identification of this cadherin-like domain indicates that the cadherin superfamily may exhibit wider sequence and structural diversity than previously appreciated. Domain architecture analysis revealed that the CHDL domain is also associated with other adhesion domains as well as enzyme domains. Based on computational analysis and previous experimental data, we predict that the CHDL domain has calcium-binding and also carbohydrate-binding activity.