Purification and characterization of the polypeptides of core light-harvesting complexes from purple sulfur bacteria.

Although the polypeptides of core light-harvesting complexes (LH1) from many purple nonsulfur bacteria have been well characterized, little information is available on the polypeptides of LH1 from purple sulfur photosynthetic organisms. We present here the results of isolation and characterization of LH1 polypeptides from two purple sulfur bacteria, Thermochromatium (Tch.) tepidum and Allochromatium (Ach.

N-terminal methylation of the core light-harvesting complex in purple photosynthetic bacteria.

Several core light-harvesting complexes from both sulfur and non-sulfur purple photosynthetic bacteria have been identified to be methylated at the N-terminal alpha-amino group of beta-polypeptides by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nuclear magnetic resonance. Monomethylation has been confirmed for the N-terminal alanine residues of the beta-polypeptides from Rhodospirillum rubrum, Thermochromatium tepidum and Chromatium vinosum, but not for the beta-polypeptide from Rhodobacter sphaeroides. The modification appears to be related with the amino acid sequence and charge distribution in the N-terminal end.

Selective detection and assignment of the solution NMR signals of bacteriochlorophyll a in a reconstituted subunit of a light-harvesting complex.

High-resolution solution NMR spectra have been obtained for bacteriochlorophyll (BChl) a molecules in a biologically functional subunit of a bacterial core light-harvesting complex based on a modified reconstitution method. The reconstituted subunit of pigment-integral membrane polypeptides is stable and homogeneous at high concentrations at room temperature and exhibits a Q(y) absorption peak at 818 nm. (1)H and (13)C chemical shifts have been specifically assigned for BChl a using the fully and selectively (13)C-labeled pigments incorporated with natural abundance polypeptides in deuterated detergent solution.