PMID:10037713
| Citation |
Kennedy, KA and Traxler, B (1999) MalK forms a dimer independent of its assembly into the MalFGK2 ATP-binding cassette transporter of Escherichia coli. J. Biol. Chem. 274:6259-64 |
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| Abstract |
The maltose transport complex (MTC) is a member of the ATP-binding cassette superfamily of membrane transport proteins and is a model for understanding the folding and assembly of hetero-oligomeric membrane protein complexes. The MTC is made up of two integral membrane proteins, MalF and MalG, and a peripheral membrane protein, MalK. These proteins associate with a stoichiometry of 1:1:2 to form the complex MalFGK2. In our studies of the oligomerization of this complex, we have shown that the ATP-binding component, MalK, forms a dimer in the absence of MalF and MalG. Epitope-tagged MalK coimmunoprecipitated with wild-type MalK, indicating that the MalK protein forms an oligomer. The relative amounts of tagged and wild-type MalK that were present in the whole cell extracts and in the immunoprecipitated complexes show that the MalK oligomer is a dimer. These hetero-oligomers can also be formed in vitro by mixing two extracts, each containing either tagged or wild-type MalK. The dimerization of MalK was also demonstrated in vivo using the bacteriophage lambda repressor fusion assay. The formation of a MalK dimer in the absence of MalF and MalG may represent an initial step in the assembly pathway of the MTC. |
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| Keywords |
ATP-Binding Cassette Transporters/chemistry; ATP-Binding Cassette Transporters/metabolism; Bacterial Proteins/chemistry; Bacterial Proteins/metabolism; Carrier Proteins/chemistry; Carrier Proteins/metabolism; Dimerization; Escherichia coli; Escherichia coli Proteins; Maltose-Binding Proteins; Monosaccharide Transport Proteins; Protein Binding |
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