Premium
A 13 C NMR study on [3‐ 13 C]‐, [1‐ 13 C]Ala‐, or [1‐ 13 C]Val‐labeled transmembrane peptides of bacteriorhodopsin in lipid bilayers: Insertion, rigid‐body motions, and local conformational fluctuations at ambient temperature
Author(s) -
Kimura Shigeki,
Naito Akira,
Tuzi Satoru,
Saitô Hazime
Publication year - 2001
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/1097-0282(200101)58:1<78::aid-bip80>3.0.co;2-c
Subject(s) - chemistry , bacteriorhodopsin , bilayer , lipid bilayer , crystallography , helix (gastropod) , transmembrane protein , transmembrane domain , chemical shift , amino acid , stereochemistry , membrane , biochemistry , ecology , receptor , snail , biology
We have recorded 13 C NMR spectra of selectively [3‐ 13 C]Ala‐, [1‐ 13 C]Ala‐, or [1‐ 13 C]Val‐labeled synthetic transmembrane peptides of bacteriorhodopsin (bR) and enzymatically cleaved C‐2 fragment in the solid and dimyristoylphosphatidylcholine bilayer. It turned out that these transmembrane peptides either in hexafluoroisopropanol or cast from it take an ordinary α‐helix (α I ‐helix) irrespective of their amino acid sequences with reference to the conformation‐dependent 13 C chemical shifts of (Ala) n taking the α‐helix form. These transmembrane peptides are not always static in the lipid bilayer as in the solid state but undergo rigid‐body motions with various frequencies as estimated from suppressed peaks either by fast isotropic or large‐amplitude motions (>10 8 Hz) or intermediate frequencies (10 5 or 10 3 Hz). Further, 13 C chemical shifts of the [3‐ 13 C]Ala‐labeled peptides in the bilayer were displaced downfield by 0.3–1.1 ppm depending upon amino acid sequence with respect to those in the solid state, which were explained in terms of local conformational fluctuation (10 2 Hz) deviated from the torsion angles (α II ‐helix) from those of standard α‐helix, under anisotropic environment in lipid bilayer, in addition to the above‐mentioned rigid‐body motions. The carbonyl 13 C peaks, on the other hand, are not sensitively displaced by such local anisotropic fluctuations, because they are more sensitive to the manner of hydrogen‐bond interactions. The amino acid sequences of these peptides inserted within the bilayer were not always the same as those of intact bR, causing disposition of the transmembrane α‐helical segment from that of intact bR. Finally, we confirmed that the 13 C NMR peak positions of the random coil form are located at the boundary between the α‐helix and a turned structure in loop regions. © 2000 John Wiley & Sons, Inc. Biopoly 58: 78–88, 2001