From bacteria to man: archaic proton-dependent peptide transporters at work.
Uptake of nutrients into cells is essential to life and occurs in all organisms at the expense of energy. Whereas in most prokaryotic and simple eukaryotic cells electrochemical transmembrane proton gradients provide the central driving force for nutrient uptake, in higher eukaryotes it is more frequently coupled to sodium movement along the transmembrane sodium gradient, occurs via uniport mechanisms driven by the substrate gradient only, or is linked to the countertransport of a similar organic solute. With the cloning of a large number of mammalian nutrient transport proteins, it became obvious that a few "archaic'' transporters that utilize a transmembrane proton gradient for nutrient transport into cells can still be found in mammals. The present review focuses on the electrogenic peptide transporters as the best studied examples of proton-dependent nutrient transporters in mammals and summarizes the most recent findings on their physiological importance. Taking peptide transport as a general phenomenon found in nature, we also include peptide transport mechanisms in bacteria, yeast, invertebrates, and lower vertebrates, which are not that often addressed in physiology journals.
Daniel
Hannelore
H
Department of Food and Nutrition, Molecular Nutrition Unit, Technical University of Munich, Freising-Weihenstephan, Germany. daniel@wzw.tum.de
Spanier
Britta
B
Kottra
Gabor
G
Weitz
Dietmar
D
D000595:Amino Acid Sequence; D000818:Animals; D001419:Bacteria; D001692:Biological Transport; D005057:Eukaryotic Cells / Q000502:physiology*; D006801:Humans; D007448:Invertebrates; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000502:physiology*; D008969:Molecular Sequence Data; D000074011:Peptide Transporter 1; D010802:Phylogeny; D011387:Prokaryotic Cells / Q000502:physiology*; D011522:Protons; D013379:Substrate Specificity; D027981:Symporters / Q000737:chemistry / Q000502:physiology; D014714:Vertebrates; D015003:Yeasts
D026901:Membrane Transport Proteins; D000074011:Peptide Transporter 1; D011522:Protons; D027981:Symporters; C093694:hydrogen-coupled oligopeptide transporter PepT2; C043912:peptide permease