Chemical crosslinking studies of the isolated light-harvesting B800-850 complex of Chromatium minutissimum.

The spatial relationship of polypeptides comprising the light-harvesting B800-850 complex of Chromatium minutissimum has been studied by means of chemical crosslinking of the isolated complex with cleavable, 1.2 nm-long dithiobis(succinimidyl propionate). The samples were analyzed by different types of electrophoresis and spectrophotometrically. No difference was shown between crosslinking of the B800-850 complex either solubilized or incorporated into proteoliposomes. It was found that two main polypeptides form only one type of heterodimer. The crosslinked complex was more thermostable. This crosslinkage restricted the conformational transitions causing the shift of the long wavelength band in the near infrared region. A structure of the complex is discussed.