ISSN:
1573-5079
Keywords:
magic angle spinning
;
membrane protein dynamics
;
membrane protein structure
;
nuclear magnetic resonance
;
photosynthetic purple bacteria
;
quadrupole echo
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The photosynthetic purple bacteria such as Rb. sphaeroides possesses an intracytoplasmic membrane (ICM) and a variety of pigment-binding membrane proteins located in the ICM, acting as photoreceptor. Such photosynthetic apparatus is concentrated in the ICM. It is composed of three multimeric membrane-bound proteins; light-harvesting complexes (LH 1, LH 2), a reaction center (RC) and a cytochrome b/c1 complex. We have purified these membranes, which are called chromatophores, and characterized the structure and dynamics of the photosynthetic membrane-bound proteins by means of multi-nuclear solid state NMR. First, the isotropic chemical shift of carbonyl carbons in natural abundance and [1-13C] Phe labeled chromatophores indicates that the membrane-bound proteins take mainly the helical conformation. Second, the chemical shifts of side-chain resonances of uniformly 15N-labeled chromatophores indicate the side-chain histidine residue is mainly hydrogen bonded, whereas structural heterogeneity of arginine and lysine side-chains are probed by those wide distribution of 15N shifts. Thirdly, the [β-2H3]Ala and [ε-2H2]Tyr labeling of the chromatophores are performed and dynamics of the [β-2H]Ala and the [ε-2H2]Tyr labeled chromatophores are studied by means of 2H solid state NMR. The dynamics of [β-2H3]Ala is found to be a 108Hz three-site jump motion with 10° liberation along the Cα-Cβ bond axis. The 2H-NMR powder pattern spectrum of [ε-2H2] Tyr labeled chromatophores was interpreted with an averaged correlation time of 5×105 Hz with 180° two-fold flips, the result of the averaging of two kinds of split spectra in terms of motional time scale.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1006428609901
Permalink