Related Experiment Video
Updated: Jun 27, 2025

Real Time Measurements of Membrane Protein:Receptor Interactions Using Surface Plasmon Resonance SPR
Published on: November 29, 2014
The substrate-binding domains of the osmoregulatory ABC importer OpuA transiently interact
Marco van den Noort1, Panagiotis Drougkas1,2, Cristina Paulino1,2
1Department of Biochemistry, Groningen Biomolecular Science and Biotechnology Institute, University of Groningen, Groningen, Netherlands.
Abstract:
Bacteria utilize various strategies to prevent internal dehydration during hypertonic stress. A common approach to countering the effects of the stress is to import compatible solutes such as glycine betaine, leading to simultaneous passive water fluxes following the osmotic gradient. OpuA from Lactococcus lactis is a type I ABC-importer that uses two substrate-binding domains (SBDs) to capture extracellular glycine betaine and deliver the substrate to the transmembrane domains for subsequent transport. OpuA senses osmotic stress via changes in the internal ionic strength and is furthermore regulated by the 2nd messenger cyclic-di-AMP. We now show, by means of solution-based single-molecule FRET and analysis with multi-parameter photon-by-photon hidden Markov modeling, that the SBDs transiently interact in an ionic strength-dependent manner. The smFRET data are in accordance with the apparent cooperativity in transport and supported by new cryo-EM data of OpuA. We propose that the physical interactions between SBDs and cooperativity in substrate delivery are part of the transport mechanism.
More Related Videos
Related Concept Videos
ABC Transporters: Importer
In bacteria, based on the number of transmembrane helices and the chemical nature of their substrates, the ABC importers can be divided into three types:
ABC Transporters: Exporter
Secondary Active Transport
Aquaporins
Primary Active Transport
The Significance of Membrane Transport
Transporters facilitate either an active or passive movement of solutes. They can allow a single-molecule transport down its...

