Va. Boichenko et Zk. Makhneva, LIGHT-INDUCED INHIBITION OF RESPIRATION AND ORGANIZATION OF PHOTOSYNTHETIC UNITS IN WHOLE CELLS OF PURPLE BACTERIA, Biochemistry, 59(8), 1994, pp. 885-890
The structural and functional organization of photosynthetic units in
various species of nonsulfur purple bacteria was studied using the act
ion spectra and effective cross-sections of absorption for light-induc
ed inhibition of respiration in whole cells. in Rhodospirillum rubrum,
which contains a complex of reaction center (RC) with B875, and Rhodo
bacter capsulatus, which contains RC complexes with B875 and B800-850
have functional photosynthetic units sizes of 27 +/- 4 and 53 +/- 6 ba
cteriochlorophyll molecules, respectively. The cells of Rhodopseudomon
as palustris AB grown under high-light and low-light conditions displa
yed different action spectra and functional antenna sizes of 44 +/- 4
and 112 +/- 13 molecules of bacteriochlorophyll, respectively. This ph
enomenon indicates that adaptive changes occurred in the pigment compo
sition of the complex B800-850 and its stoichiometry with RCs. However
, there was no considerable change in the effective absorption cross-s
ection for light-induced inhibition of respiration in Rps. palustris u
nder constant illumination that closed 50-70% of RCs or after treatmen
ts inducing Mg2+-dependent changes in cooperativity and/or protein pho
sphorylation in photosynthetic units. Concerning their function, this
means that the multicenter organization of photosynthetic units in pur
ple bacteria offers no substantial advantage over the unicentral organ
ization in terms of the effectiveness of conversion of the energy of l
ight.