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Published April 3, 2015 | public
Journal Article Open

The Allosteric Regulatory Mechanism of the Escherichia coli MetNI Methionine ATP Binding Cassette (ABC) Transporter


The MetNI methionine importer of Escherichia coli, an ATP Binding Cassette (ABC) transporter, uses the energy of ATP binding and hydrolysis to catalyze the high affinity uptake of D- and L-methionine. Early in vivo studies showed that the uptake of external methionine is repressed by the level of the internal methionine pool, a phenomenon termed transinhibition. Our understanding of MetNI mechanism has thus far been limited to a series of crystal structures in an inward facing conformation. To understand the molecular mechanism of transinhibition, we studied the kinetics of ATP hydrolysis using detergent-solubilized MetNI. We find that transinhibition is due to noncompetitive inhibition by L-methionine, much like a negative feedback loop. Thermodynamic analyses revealed two allosteric methionine binding sites per transporter. This quantitative analysis of transinhibition, the first to our knowledge for a structurally defined transporter, builds upon the previously proposed structurally based model for regulation. This mechanism of regulation at the transporter activity level could be applicable to not only ABC transporters but other types of membrane transporters as well.

Additional Information

© 2015 by The American Society for Biochemistry and Molecular Biology, Inc. Received August 7, 2014, Accepted February 12, 2015, First Published on February 12, 2015. We thank Eric Johnson and Chris Vercollone for early initial studies, Kana Takematsu for discussion regarding modeling, and Jeff Lai for technical assistance. This work was supported by NIH Grant R01 GM45162 to DCR.

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Published - 9135.full.pdf

Supplemental Material - jbc.M114.603365-1.pdf


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August 20, 2023
August 20, 2023