Polyamine transport in bacteria and yeast.
The polyamine content of cells is regulated by biosynthesis, degradation and transport. In Escherichia coli, the genes for three different polyamine transport systems have been cloned and characterized. Two uptake systems (putrescine-specific and spermidine-preferential) were ABC transporters, each consisting of a periplasmic substrate-binding protein, two transmembrane proteins and a membrane-associated ATPase. The crystal structures of the substrate-binding proteins (PotD and PotF) have been solved. They consist of two domains with an alternating beta-alpha-beta topology, similar to other periplasmic binding proteins. The polyamine-binding site is in a cleft between the two domains, as determined by crystallography and site-directed mutagenesis. Polyamines are mainly recognized by aspartic acid and glutamic acid residues, which interact with the NH(2)- (or NH-) groups, and by tryptophan and tyrosine residues that have hydrophobic interactions with the methylene groups of polyamines. The precursor of one of the substrate binding proteins, PotD, negatively regulates transcription of the operon for the spermidine-preferential uptake system, thus providing another level of regulation of cellular polyamines. The third transport system, catalysed by PotE, mediates both uptake and excretion of putrescine. Uptake of putrescine is dependent on membrane potential, whereas excretion involves an exchange reaction between putrescine and ornithine. In Saccharomyces cerevisiae, the gene for a polyamine transport protein (TPO1) was identified. The properties of this protein are similar to those of PotE, and TPO1 is located on the vacuolar membrane.
Igarashi
K
K
Faculty of Pharmaceutical Sciences, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan. iga16077@p.chiba-u.ac.jp
Kashiwagi
K
K
D000595:Amino Acid Sequence; D017920:Antiporters / Q000378:metabolism; D001419:Bacteria / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000235:genetics; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D033902:Periplasmic Binding Proteins; D011073:Polyamines / Q000378:metabolism*; D017433:Protein Structure, Secondary; D011700:Putrescine / Q000378:metabolism; D017982:Receptors, Biogenic Amine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D013095:Spermidine / Q000378:metabolism; D015003:Yeasts
D017920:Antiporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D033902:Periplasmic Binding Proteins; D011073:Polyamines; C099274:PotD protein, E coli; C071519:PotE protein, E coli; D017982:Receptors, Biogenic Amine; C049683:potF protein, E coli; D013095:Spermidine; D011700:Putrescine