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Studies of the Maltose Transport System Reveal a Mechanism for Coupling ATP Hydrolysis to Substrate Translocation without Direct Recognition of Substrate
- Source :
- Biochemistry Publications
- Publication Year :
- 2010
- Publisher :
- Elsevier BV, 2010.
-
Abstract
- The ATPase activity of the maltose transporter (MalFGK(2)) is dependent on interactions with the maltose-binding protein (MBP). To determine whether direct interactions between the translocated sugar and MalFGK(2) are important for the regulation of ATP hydrolysis, we used an MBP mutant (sMBP) that is able to bind either maltose or sucrose. We observed that maltose- and sucrose-bound sMBP stimulate equal levels of MalFGK(2) ATPase activity. Therefore, the ATPase activity of MalFGK(2) is coupled to translocation of maltose solely by interactions between MalFGK(2) and MBP. For both maltose and sucrose, the ability of sMBP to stimulate the MalFGK(2) ATPase was greatly reduced compared with wild-type MBP, indicating that the mutations in sMBP have interfered with important interactions between MBP and MalFGK(2). High resolution crystal structure analysis of sMBP shows that in the closed conformation with bound sucrose, three of four mutations are buried, and the fourth causes only a minor change in the accessible surface. In contrast, in the open form of sMBP, all of the mutations are accessible, and the main chain of Tyr(62)-Gly(69) is destabilized and occupies an alternative conformation due to the W62Y mutation. On this basis, the compromised ability of sMBP to stimulate ATP hydrolysis by MalFGK(2) is most likely due to a disruption of interactions between MalFGK(2) and the open, rather than the closed, conformation of sMBP. Modeling the open sMBP structure bound to MalFGK(2) in the transition state for ATP hydrolysis points to an important site of interaction and suggests a mechanism for coupling ATP hydrolysis to substrate translocation that is independent of the exact structure of the substrate.
- Subjects :
- Sucrose
Protein Conformation
ATPase
ATPases
ATP-binding cassette transporter
Plasma protein binding
Crystallography, X-Ray
Ligands
Chemical-Mechanical Coupling
Biochemistry
Substrate Specificity
chemistry.chemical_compound
Adenosine Triphosphate
Protein structure
ATP hydrolysis
Maltose
Molecular Biology
Adenosine Triphosphatases
Maltose transport
Dose-Response Relationship, Drug
biology
Sugar Transport
Escherichia coli Proteins
Hydrolysis
Cell Membrane
Membrane Proteins
Cell Biology
Ligand-binding Protein
ABC Transporter
Protein Transport
chemistry
Mutation
Enzymology
biology.protein
ATP-Binding Cassette Transporters
Substrate Recognition
Adenosine triphosphate
Protein Binding
Subjects
Details
- ISSN :
- 00219258
- Volume :
- 285
- Database :
- OpenAIRE
- Journal :
- Journal of Biological Chemistry
- Accession number :
- edsair.doi.dedup.....5d1bebd81b3a27e212989ec3e2d2ad60