4zir
From Proteopedia
Crystal structure of EcfAA' heterodimer bound to AMPPNP
Structural highlights
FunctionECFA2_THEMA ATP-binding (A) component of a common energy-coupling factor (ECF) ABC-transporter complex. Unlike classic ABC transporters this ECF transporter provides the energy necessary to transport a number of different substrates (Probable). Expression of the complex plus RibU in E.coli allows riboflavin uptake; uptake does not occur in the absence of RibU or the EcfA1A2T complex.[1] Publication Abstract from PubMedECF transporters are a family of active transporters for vitamins. They are composed of four subunits: a membrane-embedded substrate-binding subunit (EcfS), a transmembrane coupling subunit (EcfT) and two ATP-binding-cassette ATPases (EcfA and EcfA'). We have investigated the mechanism of the ECF transporter for riboflavin from the pathogen Listeria monocytogenes, LmECF-RibU. Using structural and biochemical approaches, we found that ATP binding to the EcfAA' ATPases drives a conformational change that dissociates the S subunit from the EcfAA'T ECF module. Upon release from the ECF module, the RibU S subunit then binds the riboflavin transport substrate. We also find that S subunits for distinct substrates compete for the ATP-bound state of the ECF module. Our results explain how ECF transporters capture the transport substrate and reproduce the in vivo observations on S-subunit competition for which the family was named. ATP binding drives substrate capture in an ECF transporter by a release-and-catch mechanism.,Karpowich NK, Song JM, Cocco N, Wang DN Nat Struct Mol Biol. 2015 Jun 8. doi: 10.1038/nsmb.3040. PMID:26052893[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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