Abstract
In polytopic alpha-helical transmembrane proteins, the distribution of amide vibrational transition moments can be nonaxial, if the helix axes are tilted relative to the symmetry axis of the helix bundle. The infrared dichroic ratios from oriented samples then contain nonaxial terms and, in the most general case, require a second-order parameter for the axis of the helix bundle. The extent of nonaxiality depends on the summation over the individual amide transition moments along the helix. Because this is strongly oscillatory, with a 3.6-residue periodicity, complete axial symmetry is not achieved rapidly on progressive summation. Expressions for the contributions of residual nonaxiality to the dichroic ratios are derived. A similar situation arises for oligomers of transmembrane beta-barrel proteins, e.g., the porin trimer. In this case, the extent of nonaxiality depends not only on the number of residues in the beta-barrel, but also on the tilt of the beta-strands relative to the barrel axis and the characteristic dimensions of a beta-sheet, which together determine the axial periodicity. The nonaxial contributions to the dichroic ratios of beta-barrel oligomers are also derived. Estimates are given of the likely size of the ...Continue Reading
References
Mar 1, 1979·Biophysical Journal·K J Rothschild, N A Clark
Feb 14, 1995·Biochemistry·N A RodionovaL K Tamm
Dec 1, 1995·Biophysical Journal·P H AxelsenR N Lewis
Citations
Apr 7, 2004·Journal of Molecular Biology·Derek Marsh
Jan 12, 2002·Current Opinion in Structural Biology·A Arora, L K Tamm
May 28, 2010·The Journal of Physical Chemistry. B·Khoi Tan NguyenZhan Chen
Aug 5, 2009·The Journal of Physical Chemistry. B·Khoi Tan NguyenZhan Chen
May 24, 2001·Biophysical Journal·T Páli, D Marsh
Dec 15, 2010·Biochimica Et Biophysica Acta·Alessio AusiliDerek Marsh
Nov 5, 1999·Biophysical Journal·D Marsh
Apr 25, 2000·Biophysical Journal·D MarshF J Schmitt
Feb 13, 2001·Biophysical Journal·D Marsh, T Páli
Mar 25, 2000·Journal of Molecular Biology·D Marsh
Jan 17, 2008·Applied Spectroscopy·Nagarajan RamakrishnanMei Lu
Mar 15, 2001·FEBS Letters·V FaivreA Baszkin
Oct 6, 2000·The Journal of Biological Chemistry·H AbrechtF Homble
Jul 7, 1999·Biochimica Et Biophysica Acta·E GoormaghtighJ M Ruysschaert
Mar 2, 2005·Biochemistry·Muthu RamakrishnanDerek Marsh
Jun 19, 2002·Biochemistry·Johannes le CoutreErnest M Wright