Modulation of the protein environment in the hydrophilic pore of the ammonia transporter protein AmtB upon GlnK protein binding.
The conduction of ammonia/ammonium (NH3/NH4(+)) through the channel protein AmtB is inhibited by the binding of the signal transduction protein GlnK. In the AmtB-GlnK binding interface, there exists an NH3/NH4(+) binding site--Am6. The calculated pK(a) values at the Am6 sites in both the AmtB-GlnK complex and isolated AmtB implies the dominance of an uncharged NH3 state. The GlnK protein binding causes a significant downshift in the Am6 pK(a) value of the AmtB. However, this downshift is perfectly compensated by the reorientation of the protein backbone (carbonyl group of Cys312 from the AmtB part) upon AmtB-GlnK complex formation.
Ishikita
Hiroshi
H
Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA. hzi@usc.edu
D000641:Ammonia / Q000378:metabolism; D001665:Binding Sites; D027682:Cation Transport Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D009713:Nucleotidyltransferases / Q000737:chemistry* / Q000378:metabolism*; D051922:PII Nitrogen Regulatory Proteins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship
C111096:AmtB protein, E coli; D027682:Cation Transport Proteins; D029968:Escherichia coli Proteins; D051922:PII Nitrogen Regulatory Proteins; D000641:Ammonia; C497878:glnK protein, E coli; D009713:Nucleotidyltransferases