Functional and Phylogenetic Classification of Membrane Transport Proteins
The 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. Curated annotations, TC numbers, and external references for 1710 families of transport proteins are provided. Transport systems are classified on the basis of five criteria, and each of these criteria corresponds to one of the five numbers or letters within the TC accession for a particular type of transporter.
(you can find more detailed information about the TC system HERE.)
Some facts about TCDB:
- » TCDB is a curated database of factual information from 21291 published references
- » The database contains 22183 protein sequences
- » These proteins are classified into 1710 transporter families based on the TC-System
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recent advances. Nucleic Acids Res. 44(D1):D372–9 
-  Saier MH, Reddy VS, Tamang DG, Vastermark A. (2014). The transporter classification database.
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-  Saier MH Jr, Yen MR, Noto K, Tamang DG, Elkan C. (2009). The Transporter Classification Database: recent advances,
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-  Saier MH Jr, Tran CV, Barabote RD. (2006). TCDB: the Transporter Classification Database for membrane transport protein
analyses and information, Nucl. Acids Res. 34:D181-6.