Table 7.

Classification of channel proteins (excluding porins) according to substrate specificity

SubstrateTC no.FamilySourceRegulation
I.A. Nonselective
 Nonselective1.A.17CSCPl
 Nonselective (slight cation-over-anion selectivity)1.A.22MscLBMechanosensitive (osmotic pressure)
 Nonselective (slight anion-over-cation selectivity)1.A.23MscSBMechanosensitive (osmotic pressure)
 Nonselective1.A.24ConnexinAn
 Nonselective1.A.25InnexinAn
 Nonselective1.A.28–1.A.43HolinB, phage
 Nonselective1.CAll toxin-type pore-forming proteins/peptidesB, A, E
I.B. Water
 Water1.A.8MIP aquaporinsB, EHormonal regulation in animals
 Water1.A.44UTAn
I.C. Cations
 Cation selective1.A.1.11VICAnVoltage sensitive
 Cation selective1.A.3.1RIR-CaCAnRyanodine sensitive
 Cation selective1.A.3.2RIR-CaCAnInositol triphosphate sensitive
 Cation selective1.A.4TRP-CCAnResponsive to pain, heat, etc.
 Cation selective1.A.5PCCAnCa2+ activated
 Cation selective1.A.6.1.2ENaCAnProton gated
 Cation selective1.A.6.2.1ENaCAn
 Cation selective1.A.7ACCAnExogenous-ATP sensitive
 Cation selective1.A.9.1LICAnAcetylcholine activated
 Cation selective1.A.9.2LICAnSerotonin activated
 Cation selective1.A.10.1.3GICAnExogenous-glutamate sensitive
 Cation selective1.A.13GramicidinB
 Cation selective1.A.14NSCC1An
 Cation selective1.A.15NSCC2E (Y, F, An)
 Cation selective1.A.16Mid1YStretch activated
 Cation selective1.A.26SATPl
 H+1.A.19IVCAn (virus)
 H+1.A.20CybBAn, PlArachidonate
 H+1.A.45MotB
 K+1.A.1.1–9VICB, A, Y, An, PlVoltage sensitive; Ca2+ activated; cyclic nucleotide gated
 K+1.A.2IRK-CAnATP regulated; G protein regulated; voltage sensitive
 Na+1.A.1.10VICAnVoltage sensitive
 Na+1.A.6.1.1ENaCAnLigand regulated
 Na+1.A.6.3.1ENaCAnPeptide ligand regulated
 Na+1.A.45MotB
 Na+, K+, (Ca2+) selective1.A.10GICAnGlutamate gated
 NH4+1.A.26SATPl
I.D. Anions
 Cl1.A.9.3LICAnGlycine inhibited
 Cl1.A.9.4LICAnGlutamate inhibited
 Cl1.A.9.5LICAnγ-Aminobutyrate inhibited
 Cl1.A.12O-ClCAnVoltage regulated
 Cl1.A.13E-ClCAn; B?Ca2+-calmodulin kinase regulated
 Cl (anion selective)1.A.11ClCB, A, EVoltage regulated
 Cl (anion selective)1.A.16Tic110Pl
 Cl (anion selective)1.A.27PLMAnHyperpolarization activated
II.A. Sugars and polyols
 Glycerol1.A.8MIP-glycerolB, EGlycerol inducible in bacteria
 Propanediol1.A.8MIP-glycerolB, EGlycerol inducible in bacteria
II.B. Monocarboxylates
 Organic anions1.A.27PLMAnHyperpolarization activated
 Gluconate1.A.27PLMAnHyperpolarization activated
 Glutamate1.A.27PLMAnHyperpolarization activated
 Isethionate1.A.27PLMAnHyperpolarization activated
 Lactate1.A.27PLMAnHyperpolarization activated
 Taurine1.A.27PLMAnHyperpolarization activated
III.B.  Amines, amides, and polyamines
 Methylammonium1.A.26SATPl
 Urea1.A.8MIPB
 Urea1.A.44UTAn
VII.B. Proteins
 Autolysins1.A.28–1.A.43HolinB, phage
 Botulinum toxin, L-chaina1.C.8.1.1BTTB
 Cytochrome c1.A.21Bcl-2An
 Diphtheria toxin, A-chaina1.C.7.1.1DTB
 Nucleases1.A.34.3HolinB
 Proteins1.A.18Tic110Pl
 Tetanus toxin, L-chaina1.C.8.1.2BTTB
 Thioredoxin1.A.22.1.1MscLBOsmotic downshift
  • a These toxins in TC category 1.C function to import proteins into the host cell.