Transporter Classification Database: TCDB

• UCSD (University of California San Diego)

This freely accessible database details a comprehensive IUBMB approved classification system for membrane transport proteins known as the Transporter Classification (TC) system. The TC system is analogous to the Enzyme Commission (EC) system for classification of enzymes, except that it incorporates both functional and phylogenetic information for organisms of all types. As of August 1, 2021, TCDB consists of 22,132 proteins classified in 17,390 transport systems with 1,604 tabulated 3D structures, 21,174 reference citations describing 1,708 transporter families, of which 25% are members of 94 recognized superfamilies. Overall, this is an increase of over 50% since the last published update of the database in 2016. The most recent update of the database contents and features include (1) adoption of a chemical ontology for substrates of transporters, (2) inclusion of new superfamilies, (3) a domain-based characterization of transporter families (tcDoms) for the identification of new members as well as functional and evolutionary relationships between families, (4) development of novel software to facilitate curation and use of the database, (5) addition of new subclasses of transport systems including 11 novel types of channels and 3 types of group translocators, and (6) the inclusion of many man-made (artificial) transmembrane pores/channels and carriers.