PMID:11150310
| Citation |
Mannering, DE, Sharma, S and Davidson, AL (2001) Demonstration of conformational changes associated with activation of the maltose transport complex. J. Biol. Chem. 276:12362-8 |
|---|---|
| Abstract |
In Escherichia coli, interaction of a periplasmic maltose-binding protein with a membrane-associated ATP-binding cassette transporter stimulates ATP hydrolysis, resulting in translocation of maltose into the cell. The maltose transporter contains two transmembrane subunits, MalF and MalG, and two copies of a nucleotide-hydrolyzing subunit, MalK. Mutant transport complexes that function in the absence of binding protein are thought to be stabilized in an ATPase-active conformation. To probe the conformation of the nucleotide-binding site and to gain an understanding of the nature of the conformational changes that lead to activation, cysteine 40 within the Walker A motif of the MalK subunit was modified by the fluorophore 2-(4'-maleimidoanilino)naphthalene-6-sulfonic acid. Fluorescence differences indicated that residues involved in nucleotide binding were less accessible to aqueous solvent in the binding protein independent transporter than in the wild-type transporter. Similar differences in fluorescence were seen when a vanadate-trapped transition state conformation was compared with the ground state in the wild-type transporter. Our results and recent crystal structures are consistent with a model in which activation of ATPase activity is associated with conformational changes that bring the two MalK subunits closer together, completing the nucleotide-binding sites and burying ATP in the interface. |
| Links |
PubMed Online version:10.1074/jbc.M011686200 |
| Keywords |
ATP-Binding Cassette Transporters; Adenosine Triphosphatases/metabolism; Bacterial Proteins; Carrier Proteins/chemistry; Carrier Proteins/metabolism; Escherichia coli Proteins; Maltose/metabolism; Maltose-Binding Proteins; Monosaccharide Transport Proteins; Periplasmic Binding Proteins; Protein Conformation; Solvents; Spectrometry, Fluorescence |
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