Transporter Classification database

# Overview
Transporter Classification database is an IUBMB approved classification system for membrane transport proteins including ion channels. This classification system was designed to be analogous to the EC number system for classifying enzymes, but it also uses phylogenetic information.
The upper level of classification and some examples of proteins with known 3D structure:
1. Channels/Pores
- Voltage-gated ion channel like, including potassium channels KcsA and KvAP, and inward-rectifier potassium ion channel Kirbac 
Large-conductance mechanosensitive channel, MscL 
Small-conductance mechanosensitive ion channel (MscS) 
CorA metal ion transporters  
Ligand-gated ion channel of neurotransmitter receptors (acetylcholine receptor) 
Aquaporins 
Chloride channels 
Outer membrane auxiliary proteins (polysaccharide transporter) 
Porins and some other beta barrel proteins of outer membranes
- Voltage-gated ion channel like, including potassium channels KcsA and KvAP, and inward-rectifier potassium ion channel Kirbac 
- Large-conductance mechanosensitive channel, MscL 
- Small-conductance mechanosensitive ion channel (MscS) 
- CorA metal ion transporters  
- Ligand-gated ion channel of neurotransmitter receptors (acetylcholine receptor) 
- Aquaporins 
- Chloride channels 
- Outer membrane auxiliary proteins (polysaccharide transporter) 
- Porins and some other beta barrel proteins of outer membranes
2. Electrochemical Potential-driven transporters
- Mitochondrial carrier proteins 
Major Facilitator Superfamily  (Glycerol-3-hosphate transporter, Lactose permease, and Multidrug transporter EmrD)  
Resistance-nodulation-cell division (multidrug efflux transporter AcrB, see multidrug resistance)
Dicarboxylate/amino acid:cation symporter (proton glutamate symporter)  
Monovalent cation/proton antiporter (Sodium/proton antiporter 1 NhaA) 
Neurotransmitter sodium symporter 
Ammonia transporters 
Drug/Metabolite Transporter  (small multidrug resistance transporter EmrE - the structures  are retracted as erroneous) 
- Mitochondrial carrier proteins 
- Major Facilitator Superfamily  (Glycerol-3-hosphate transporter, Lactose permease, and Multidrug transporter EmrD)  
- Resistance-nodulation-cell division (multidrug efflux transporter AcrB, see multidrug resistance)
- Dicarboxylate/amino acid:cation symporter (proton glutamate symporter)  
- Monovalent cation/proton antiporter (Sodium/proton antiporter 1 NhaA) 
- Neurotransmitter sodium symporter 
- Ammonia transporters 
- Drug/Metabolite Transporter  (small multidrug resistance transporter EmrE - the structures  are retracted as erroneous) 
3. Primary Active Transporters
- Light absorption-driven transporters:
Bacteriorhodopsin-like proteins including rhodopsin (see also opsin)
Bacterial photosynthetic reaction centres and photosystems I and II 
Light harvesting complexes from bacteria and chloroplasts 
- Bacteriorhodopsin-like proteins including rhodopsin (see also opsin)
- Bacterial photosynthetic reaction centres and photosystems I and II 
- Light harvesting complexes from bacteria and chloroplasts 
- Oxidoreduction-driven transporters
Transmembrane cytochrome b-like proteins : coenzyme Q - cytochrome c reductase (cytochrome bc1 ); cytochrome b6f  complex; formate dehydrogenase, respiratory nitrate reductase; succinate - coenzyme Q reductase (fumarate reductase); and succinate dehydrogenase.  See electron transport chain.
Cytochrome c oxidases  from bacteria and mitochondria
- Transmembrane cytochrome b-like proteins : coenzyme Q - cytochrome c reductase (cytochrome bc1 ); cytochrome b6f  complex; formate dehydrogenase, respiratory nitrate reductase; succinate - coenzyme Q reductase (fumarate reductase); and succinate dehydrogenase.  See electron transport chain.
- Cytochrome c oxidases  from bacteria and mitochondria
- Electrochemical potential-driven transporters
Proton or sodium translocating F-type and V-type ATPases 
- Proton or sodium translocating F-type and V-type ATPases 
- P-P-bond hydrolysis-driven transporters
P-type calcium ATPase  (five different conformations)  
Calcium ATPase regulators phospholamban and sarcolipin
ABC transporters: BtuCD, multidrug transporter, and  molybdate uptake transporter
General secretory pathway (Sec) translocon (preprotein translocase SecY) 
- P-type calcium ATPase  (five different conformations)  
- Calcium ATPase regulators phospholamban and sarcolipin
- ABC transporters: BtuCD, multidrug transporter, and  molybdate uptake transporter
- General secretory pathway (Sec) translocon (preprotein translocase SecY) 
4. Group Translocators
5. Transport Electron Carriers
- Disulfide bond formation protein B (DsbB) 
- Disulfide bond formation protein B (DsbB) 
8. Accessory Factors Involved in Transport
9. Incompletely Characterized Transport Systems

# Examples
- Cystic fibrosis transmembrane conductance regulator --  3.A.1.202.1