Membrane Transport Proteins

Practically all the material presented here is based on the work of Milton H. Saier Jr. of the University of California in San Diego and of his co-workers. Detailed treatment of the various families and their individual members can be found at http://www.tcdb.org. The principles of the document were discussed by a panel of the Nomenclature Committee of the IUBMB and it was prepared for publication by Arnost Kotyk, Academy of Sciences of the Czech Republic, Prague. Additions and corrections agreed in 2003 have been applied. [Copyright IUBMB]

Any comments should be sent to any member of the Committee

• Introduction
• Glossary of terms used in membrane transport work
• List of families and subfamilies of the TC system
  • 1. Pores and channels
    • 1.A a-Helical channels
    • 1.B b-Strand porins
    • 1.C Pore-forming toxins
    • 1.D Non-ribosomally synthesized channels
    • 1.E Holins
  • 2. Electrochemical-potential-driven transporters
    • 2.A Transporters or carriers (uniporters, symporters and antiporters)
    • 2.B Non-ribosomally synthesized transporters
  • 3. Primary active transporters
    • 3.A P-P-bond-hydrolysis-driven transporters
    • 3.B Decarboxylation-driven transporters
    • 3.C Methyl-transfer-driven transporters
    • 3.D Oxidoreduction-driven transporters
    • 3.E Light-driven transporters
  • 4. Group translocators
  • 5. Transmembrane electron carriers
  • 8. Accessory factors involved in transport
  • 9. Incompletely characterized transport systems
• Properties of families of transport proteins included in the TC system
  • 1. Pores and channels
    • 1.A a-Helical channels
    • 1.B b-Strand porins
    • 1.C Pore-forming toxins
    • 1.D Non-ribosomally synthesized channels
    • 1.E Holins
  • 2. Electrochemical-potential-driven transporters
    • 2.A Transporters or carriers (uniporters, symporters and antiporters)
    • 2.B Non-ribosomally synthesized transporters
  • 3. Primary active transporters
    • 3.A P-P-bond-hydrolysis-driven transporters
    • 3.B Decarboxylation-driven transporters
    • 3.C Methyl-transfer-driven transporters
    • 3.D Oxidoreduction-driven transporters
    • 3.E Light-driven transporters
  • 4. Group translocators
    • 4.A Phosphotransferases
  • 5. Transmembrane electron carriers
    • 5.A Two-electron carriers
    • 5.B One-electron carriers
  • 8. Accessory factors involved in transport
    • 8.A Auxiliary transport proteins
  • 9. Incompletely characterized transport systems
    • 9.A Transporters of unknown classification
• Classification of transport proteins according to substrate specificity
  • 1. Channel proteins (excluding porins)
    • I.A. Nonselective
    • I.B. Water
    • I.C. Cations
    • I.D Anions
    • II.A. Sugars and polyols
    • II.B. Monocarboxylates
    • III.B. Amines, amides, and polyamines
    • VII.B. Proteins
  • 2. Outer membrane porins (most from Gram-negative bacteria)
    • I.A. Nonselective
    • I.C. Cations
    • I.D. Anions
    • II.A. Sugars and polyols
    • II.B. Monocarboxylates
    • II.E. Others
    • III.A. Amides
    • IV.B. Nucleosides
    • IV.C. Nucleotides
    • V.A. Vitamins
    • V.B. Enzyme and redox cofactors
    • V.C. Iron-siderophores
    • VI.A. Multiple drugs
    • VII.A. Carbohydrates
    • VII.B. Proteins
  • 3. Uniporters, symporters and antiporters
    • I.C. Inorganic cations
    • I.D. Inorganic anions
    • II.A. Sugars and polyols
    • II.B. Monocarboxylates
    • II.C. Di- and tricarboxylates
    • II.D. Organic anions (noncarboxylates)
    • III.A. Amino acids and conjugates
    • III.B. Amines, amides, and polyamines
    • III.C. Peptides
    • IV.A. Nucleobases
    • IV.B. Nucleosides
    • IV.C. Nucleotides
    • V.A. Vitamins/cofactor precursors
    • V.B. Enzyme and redox cofactors
    • V.C. Siderophores and Fe-siderophore complexes
    • V.D. Signaling molecules
    • VI.A. Multiple drugs and dyes
    • VI.B. Specific drugs
    • VI.C. Bile salts and conjugates
    • VI.D. Sterols/steroids
    • VII.A. Carbohydrates
    • VII.B. Proteins
    • VII.D. Lipids
  • 4. Primary active transporters (excluding macromolecular transporters)
    • I.C.1. Inorganic cations: univalent
    • I.C.2. Inorganic cations: divalent and tervalent
    • I.D. Inorganic anions
    • II.A. Sugars and polyols
    • II.B. Fatty acids
    • II.D. Organic anions: phosphates, phosphonates, sulfonates (uptake)
    • III.A. Amino acids and derivatives (uptake)
    • III.C. Peptides
    • V.A. Vitamins
    • V.B. Enzyme and redox cofactors
    • V.C. Siderophores and Fe-siderophore complexes
    • VI.A. Multiple drugs (mostly efflux)
    • VI.B. Specific drugs (mostly efflux)
    • VI.C. Bile salts and conjugates
    • VI.D. Sterols and conjugates
  • 5. Cellular macromolecular export systems (excluding porins)
    • VII.A. Carbohydrates
    • VII.B. Proteins
    • VII.C. Nucleic acids
    • VII.D. Lipids