Full engagement of liganded maltose-binding protein stabilizes a semi-open ATP-binding cassette dimer in the maltose transporter.
MalFGK2 is an ATP-binding cassette (ABC) transporter that mediates the uptake of maltose/maltodextrins into Escherichia coli. A periplasmic maltose-binding protein (MBP) delivers maltose to the transmembrane subunits (MalFG) and stimulates the ATPase activity of the cytoplasmic nucleotide-binding subunits (MalK dimer). This MBP-stimulated ATPase activity is independent of maltose for purified transporter in detergent micelles. However, when the transporter is reconstituted in membrane bilayers, only the liganded form of MBP efficiently stimulates its activity. To investigate the mechanism of maltose stimulation, electron paramagnetic resonance spectroscopy was used to study the interactions between the transporter and MBP in nanodiscs and in detergent. We found that full engagement of both lobes of maltose-bound MBP unto MalFGK2 is facilitated by nucleotides and stabilizes a semi-open MalK dimer. Maltose-bound MBP promotes the transition to the semi-open state of MalK when the transporter is in the membrane, whereas such regulation does not require maltose in detergent. We suggest that stabilization of the semi-open MalK2 conformation by maltose-bound MBP is key to the coupling of maltose transport to ATP hydrolysis in vivo, because it facilitates the progression of the MalK dimer from the open to the semi-open conformation, from which it can proceed to hydrolyze ATP.
Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA.
Frances Joan D
FJ
Alvarez
Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA.
Cédric
C
Orelle
Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA.
Yan
Y
Huang
Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA.
Ruchika
R
Bajaj
Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA.
R Michael
RM
Everly
Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, 53226, USA.
Candice S
CS
Klug
Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA.
Amy L
AL
Davidson
D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001692:Biological Transport / Q000235:genetics; D003460:Crystallization; D003902:Detergents; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006868:Hydrolysis; D008024:Ligands; D008320:Maltose / Q000378:metabolism* / Q000494:pharmacology; D058619:Maltose-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D033902:Periplasmic Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
D018528:ATP-Binding Cassette Transporters; D003902:Detergents; D029968:Escherichia coli Proteins; D008024:Ligands; C461619:MalE protein, E coli; D058619:Maltose-Binding Proteins; D033902:Periplasmic Binding Proteins; C461599:maltose transport system, E coli; D008320:Maltose; D000255:Adenosine Triphosphate