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Real Time Measurements of Membrane Protein:Receptor Interactions Using Surface Plasmon Resonance (SPR)
Published on: November 29, 2014
Structures of the substrate-binding protein provide insights into the multiple compatible solute binding
Yang Du1, Wei-Wei Shi, Yong-Xing He
1Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, People's Republic of China.
Abstract:
The compatible solute ABC (ATP-binding cassette) transporters are indispensable for acquiring a variety of compatible solutes under osmotic stress in Bacillus subtilis. The substrate-binding protein OpuCC (Opu is osmoprotectant uptake) of the ABC transporter OpuC can recognize a broad spectrum of compatible solutes, compared with its 70% sequence-identical paralogue OpuBC that can solely bind choline. To explore the structural basis of this difference of substrate specificity, we determined crystal structures of OpuCC in the apo-form and in complex with carnitine, glycine betaine, choline and ectoine respectively. OpuCC is composed of two α/β/α globular sandwich domains linked by two hinge regions, with a substrate-binding pocket located at the interdomain cleft. Upon substrate binding, the two domains shift towards each other to trap the substrate. Comparative structural analysis revealed a plastic pocket that fits various compatible solutes, which attributes themultiple-substrate binding property to OpuCC. This plasticity is a gain-of-function via a single-residue mutation of Thr⁹⁴ in OpuCC compared with Asp⁹⁶ in OpuBC.
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