The Na⁺/L-proline transporter PutP.
The Na⁺/L-proline transporter PutP is a member of the Na⁺/solute symporter family (TC 2A.21, SLC5), which contains several hundred proteins of pro- and eukaryotic origin. Within the family, the capability of L-proline uptake is restricted to proteins of prokaryotes. PutP contributes to the use of L-proline as a nutrient. In addition, the transporter may supply cells with compatible solute during adaptation to osmotic stress. Based on these and other functions, PutP is of significance for various bacteria-host interactions including the virulence of human pathogens. A homology model of Escherichia coli PutP was generated based on the crystal structure of the Vibrio parahaemolyticus Na+/galactose symporter. According to the model, PutP has a core structure of five plus five transmembrane domains forming an inverted repeat similar as originally revealed by the crystal structure of the Na+/leucine transporter LeuT. The homology model is experimentally verified by Cys cross-linking and site-directed spin labeling in combination with electron paramagnetic resonance spectroscopy. The putative sites of Na⁺ and L-proline binding are described, and a putative transport mechanism is discussed.
LMU Munich, Biocentre, Microbiology, Grosshaderner Strasse 2-4, Martinsried, D-82152, Germany. hjung@lmu.de
Heinrich
H
Jung
Daniel
D
Hilger
Michael
M
Raba
D026921:Amino Acid Transport Systems, Neutral / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001419:Bacteria / Q000378:metabolism / Q000472:pathogenicity; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D006801:Humans; D008958:Models, Molecular; D011392:Proline / Q000378:metabolism; D011487:Protein Conformation; D012964:Sodium / Q000378:metabolism; D027981:Symporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D026921:Amino Acid Transport Systems, Neutral; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D027981:Symporters; C060609:PutP protein, E coli; D011392:Proline; D012964:Sodium