3 years ago

Complex Stability During the Transport Cycle of a Subclass I ECF Transporter

Complex Stability During the Transport Cycle of a Subclass I ECF Transporter
Friedrich Finkenwirth, Thomas Eitinger, Franziska Kirsch
The mechanism of energy-coupling factor (ECF) transporters, a special type of ATP-binding-cassette importers for micronutrients in prokaryotes, is a matter of controversial discussion. Among subclass II ECF transporters, a single ECF interacts with several substrate-binding integral membrane proteins (S units) for individual solutes. Release and catch of the S unit, previously observed experimentally for a subclass II system, was proposed as the mechanism of all ECF transporters. The BioM2NY biotin transporter is a prototype of subclass I systems, among which the S unit is dedicated to a specific ECF. Here we simulated the transport cycle using purified BioM2NY in detergent solution. BioM2NY complexes were stable during all steps. ATP binding was a prerequisite for biotin capture and ATP hydrolysis for subsequent biotin release. The data demonstrate that S units of subclass I ECF transporters do not have to dissociate from holotransporter complexes for high-affinity substrate binding, indicating mechanistic differences between the two subclasses.

Publisher URL: http://dx.doi.org/10.1021/acs.biochem.7b00390

DOI: 10.1021/acs.biochem.7b00390

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