The crystal structure of UehA in complex with ectoine-A comparison with other TRAP-T binding proteins.
Substrate-binding proteins or extracellular solute receptors (ESRs) are components of both ABC (ATP binding cassette) and TRAP-T (tripartite ATP-independent periplasmic transporter). The TRAP-T system UehABC from Silicibacter pomeroyi DSS-3 imports the compatible solutes ectoine and 5-hydroxyectoine as nutrients. UehA, the ESR of the UehABC operon, binds both ectoine and 5-hydroxyectoine with high affinity (K(d) values of 1.4+/-0.1 and 1.1+/-0.1 microM, respectively) and delivers them to the TRAP-T complex. The crystal structure of UehA in complex with ectoine was determined at 2.9-A resolution and revealed an overall fold common for all ESR proteins from TRAP systems determined so far. A comparison of the recently described structure of TeaA from Halomonas elongata and an ectoine-binding protein (EhuB) from an ABC transporter revealed a conserved ligand binding mode that involves both directed and cation-pi interactions. Furthermore, a comparison with other known TRAP-T ESRs revealed a helix that might act as a selectivity filter imposing restraints on the ESRs that fine-tune ligand recognition and binding and finally might determine the selection of the cognate substrate.
Lecher
Justin
J
Institute of Biochemistry, Heinrich-Heine-University Duesseldorf, Germany.
Pittelkow
Marco
M
Zobel
Silke
S
Bursy
Jan
J
Bönig
Tobias
T
Smits
Sander H J
SH
Schmitt
Lutz
L
Bremer
Erhard
E
D000599:Amino Acids, Diamino / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000302:isolation & purification; D001665:Binding Sites; D001692:Biological Transport; D018360:Crystallography, X-Ray; D016680:Genome, Bacterial; D020632:Halomonas / Q000737:chemistry; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D011485:Protein Binding; D017433:Protein Structure, Secondary; D041902:Rhodobacteraceae / Q000201:enzymology / Q000235:genetics; D013379:Substrate Specificity
D000599:Amino Acids, Diamino; D001426:Bacterial Proteins; D008024:Ligands; C121557:hydroxyectoine; C045628:ectoine