The IUBMB-Endorsed Transporter Classification System
Transport systems are essential to every living cell. They (1) allow the entry of all essential nutrients into the cell and its compartments, (2) regulate the cytoplasmic concentrations of metabolites by excretion mechanisms, (3) provide physiological cellular concentrations of ions that can differ by several orders of magnitude from those in the external medium, (4) export macromolecules such as complex carbohydrates, proteins, lipids, and DNA, (5) catalyze export and uptake of signaling molecules that mediate intercellular communications, (6) prevent toxic effects of drugs and toxins by mediating active efflux, and (7) participate in biological warfare by exporting biological active agents that insert into or permeate the membranes of target cells. Transport is an essential aspect of all life-endowing processes: metabolism, communication, biosynthesis, reproduction, and both cooperative and antagonistic interorganismal behaviors.
KeywordsSugar Carbohydrate Polypeptide Macromolecule Nucleoside
- 1.Saier, M. H., Jr. (1998) Molecular phylogeny as a basis for the classification of transport proteins from bacteria, archaea and eukarya, in Advances in Microbial Physiology (Poole, R. K., ed.), Academic, San Diego, CA, pp. 81–136.Google Scholar
- 5.Saier, M. H., Jr. (2001) Evolution of transport proteins, in Genetic Engineering. Principles and Methods, Vol. 23 (J. K. Setlow, ed.), Kluwer Academic/Plenum, New York, pp. 1–10.Google Scholar
- 8.Saier, M. H., Jr. and T.-T. Tseng (1999) Evolutionary origins of transmembrane transport systems, in Transport of Molecules Across Microbial Membranes, Symposium 58, Society for General Microbiology (Broome-Smith, J. K., Baumberg, S., Stirling, C. J., et al., eds.), Cambridge University Press, Cambridge, UK, pp. 252–274.Google Scholar
- 10.Zhai, Y. and Saier, M. H., Jr. (2001) A web-based program (WHAT) for the simultaneous prediction of hydropathy, amphipathicity, secondary structure and transmembrane topology for a single protein sequence. J. Mol. Microbiol. Biotechnol. 4, 501–502.Google Scholar
- 13.Faergeman, N. J., Black, P. N., Zhao, X. D., et al. (2001) The acyl-CoA synthetases encoded within FAA1 and FAA4 in Saccharomyces cerevisiae function as components of the fatty acid transport system linking import, activation, and intracellular utilization. J. Biol. Chem. 276, 37,051–37,059PubMedCrossRefGoogle Scholar