* To whom correspondence should be addressed.
Received November 7, 2018; Revised November 7, 2018; Accepted November 30, 2018
This review focuses on recent experimental data obtained by site-directed mutagenesis of the reaction center in purple nonsulfur bacteria. The role of axial ligation of (bacterio)chlorophylls in the regulation of spectral and redox properties of these pigments, as well as correlation between the structure of chromophores and nature of their ligands, are discussed. Cofactor ligation in various types of reaction centers is compared, and possible reasons for observed differences are examined in the light of modern ideas on the evolution of photosynthesis.
KEY WORDS: bacteriochlorophyll ligation, photosynthetic reaction center, pigment–protein interactions, purple bacteria, site-directed mutagenesis, Rhodobacter sphaeroides