The availability of experimentally solved structures of transmembrane transporters is sparse. First, we expanded the structural knowledge of CPA/AT transporters by using integrated topology annotation and protein modelling approaches. It combines evolution guided transmembrane topology prediction, difference in positively charged residues present in inside and outside loops in alternative topological models, homology- and ab initio protein modelling approaches. A few evolutionary related Pfam families were added to Pfam CPA/AT clan to form the CPA/AT transporter dataset. It includes 23 protein families. CPA/AT transporters are classified into 4 fold-types based on their structure; (1) CPA-Broken fold-type (2) CPA-Reentrant fold-type, (3) BART fold-type, and (4) Reentrant-helix-reentrant fold-type.

The CPAfold database can be useful to experimentalists interested in studying the structure, function, mutation and design of any protein belonging to this fold. 3D structure models are available for all the families in this fold. Functional and mutational studies can be supported by these models. Novel reentrant motifs for the reentrant type transporters have been identified. Full length and repeat level topology and sequence alignments of a particular protein family with all the other families in the fold are provided. This becomes helpful for comparison of structure and function of related families of interest. The alignments are very easy to follow figures with topology being mapped on to the sequence alignment. Other details such as representative sequences, topology, multiple sequence alignments, Core and scaffold domain annotation, KR-bias, fold-type classifications etc. are also available.