| Autor: |
Bertalan É; Department of Mathematics and Natural Sciences, RWTH Aachen University, Templergraben 59, 52062 Aachen, Germany., Konno M; The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwano-ha, Kashiwa 277-8581, Chiba, Japan., Del Carmen Marín M; The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwano-ha, Kashiwa 277-8581, Chiba, Japan., Bagherzadeh R; The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwano-ha, Kashiwa 277-8581, Chiba, Japan., Nagata T; The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwano-ha, Kashiwa 277-8581, Chiba, Japan., Brown L; Department of Physics, University of Guelph, 488 Gordon Street, Guelph, Ontario N1G 2W1, Canada., Inoue K; The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwano-ha, Kashiwa 277-8581, Chiba, Japan., Bondar AN; Institute of Computational Biomedicine, Forschungszentrum Jülich, IAS-5/INM-9, Wilhelm-Johnen Straße, 5428 Jülich, Germany.; Faculty of Physics, University of Bucharest, Atomiştilor 405, 077125 Măgurele, Romania. |
| Abstrakt: |
Microbial pump rhodopsins are highly versatile light-driven membrane proteins that couple protein conformational dynamics with ion translocation across the cell membranes. Understanding how microbial pump rhodopsins use specific amino acid residues at key functional sites to control ion selectivity and ion pumping direction is of general interest for membrane transporters, and could guide site-directed mutagenesis for optogenetics applications. To enable direct comparisons between proteins with different sequences we implement, for the first time, a unique n umbering s cheme for the m icrobial pump rho dopsin residues, NS-mrho . We use NS-mrho to show that distinct microbial pump rhodopsins typically have hydrogen-bond networks that are less conserved than anticipated from the amino acid residue conservation, whereas their hydrophobic interaction networks are largely conserved. To illustrate the role of the hydrogen-bond networks as structural elements that determine the functionality of microbial pump rhodopsins, we performed experiments, atomic-level simulations, and hydrogen bond network analyses on GR, the outward proton pump from Gloeobacter violaceus , and KR2, the outward sodium pump from Krokinobacter eikastus . The experiments indicate that multiple mutations that recover KR2 amino acid residues in GR not only fail to convert it into a sodium pump, but completely inactivate GR by abolishing photoisomerization of the retinal chromophore. This observation could be attributed to the drastically altered hydrogen-bond interaction network identified with simulations and network analyses. Taken together, our findings suggest that functional specificity could be encoded in the collective hydrogen-bond network of microbial pump rhodopsins. |
