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Rhodamine6G and Hœchst33342 narrow BmrA conformational spectrum for a more efficient use of ATP.
Nat Commun, 16(1):1745.
Multidrug ABC transporters harness the energy of ATP binding and hydrolysis totranslocate substrates out of the cell and detoxify them. While this involves awell-accepted alternating access mechanism, molecular details of this interplayare still elusive. Rhodamine6G binding on a catalytic inactive mutant of thehomodimeric multidrug ABC transporter BmrA triggers a cooperative binding of ATPon the two identical nucleotide-binding-sites, otherwise michaelian. Here, weinvestigate this asymmetric behavior via a structural-enzymology approach,solving cryoEM structures of BmrA at defined ATP ratios, highlighting theplasticity of BmrA as it undergoes the transition from inward to outward facingconformations. Analysis of continuous heterogeneity within cryoEM data andstructural dynamics, reveals that Rhodamine6G narrows the conformational spectrumexplored by the nucleotide-binding domains. We observe the same behavior for theother drug Hœchst33342. Following on these findings, the effect of drug-bindingshowed an ATPase stimulation and a maximal transport activity of the wild-typeprotein at the concentration-range where the cooperative transition occurs.Altogether, these findings provide a description of the influence of drug bindingon the ATP-binding sites through a change in conformational dynamics.
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