MOLECULAR MOVIE (pp. 645-648;649-653;653-657; News & Views)
Three papers this week Nature Vol. 406, Issue 6796 (August 10, 2000) complete the first motion picture of a microbial proton pump, 'bacteriorhodopsin', in action. This small protein, from the cell membrane of a salt-loving microorganism that pumps protons out of cells and provides them with the energy to live, has been under scrutiny for 30 years. Its study has driven the development of some of the most advanced techniques in biochemistry, biophysics and structural biology.
Three groups present structures of the protein, showing how its shape changes as it goes about its proton-shunting business. The groups are: Ehud M. Landau of the University of Basel, Switzerland, and colleagues; Georg Büldt of the Institute of Structural Biology, Research Centre Jülich, Germany, and colleagues; and Sriram Subramaniam and Richard Henderson of the MRC Laboratory of Molecular Biology, Cambridge, UK, and the National Cancer Institutes, Bethesda, Maryland, USA, respectively.
Bacteriorhodopsin enables an exotic organism to flourish at unhealthy salt concentrations, using sunlight as the sole source of energy. But it is also a simple model for certain cell-membrane receptors, 'G-protein coupled seven-helix' receptors, which include most well known drug targets in humans and which probably operate by a similar switch mechanism. And it is the prototype 'membrane transporter'. These are biological macromolecules that carry out the amazing and essential feat of transporting ions against a large electrochemical potential.
"The molecular mechanism of proton pumping by bacteriorhodopsin will be an inspiration for the study of other equally fascinating but considerably more complex membrane transporters," says Werner Kühlbrandt of the Max Planck Institute of Biophysics, Frankfurt am Main, Germany, in an accompanying News and Views article.
Ehud M Landau (currently at the University of Texas)
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(C) Nature press release.
Links to pdf files of the articles are given below:
Helix deformation is coupled to vectorial proton transport in the photocycle of bacteriorhodopsin. ANTOINE ROYANT, KARL EDMAN, THOMAS URSBY, EVA PEBAY-PEYROULA, EHUD M. LANDAU & RICHARD NEUTZE (645-648).
Structural alterations for proton translocation in the M state of wild-type bacteriorhodopsin. HANS JÜRGEN SASS, GEORG BÜLDT, RALF GESSENICH, DOMINIC HEHN, DIRK NEFF, RAMONA SCHLESINGER, JOEL BERENDZEN & PAL ORMOS (pp. 649-653).
Molecular mechanism of vectorial proton translocation by bacteriorhodopsin. SRIRAM SUBRAMANIAM AND RICHARD HENDERSON (pp. 653-657).
Bacteriorhodopsin - the movie. WERNER KÜHLBRANDT (p. 569).
Message posted by: Trevor M. D'Souza