Cyclopropane-ring formation in the acyl groups of chlorosome glycolipids is crucial for acid resistance of green bacterial antenna systems

• Published in: Bioorganic & medicinal chemistry 2013-07, Vol.21 (13), p.3689-3694
• Main Authors: Mizoguchi, Tadashi, Tsukatani, Yusuke, Harada, Jiro, Takasaki, Shin, Yoshitomi, Taichi, Tamiaki, Hitoshi
• Format: Article
• Language: English
• Subjects: acid tolerance; Acylation; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; Bacteriochlorophyll; Bacteriochlorophylls - chemistry; Bacteriochlorophylls - metabolism; chemistry; Chlorobaculum tepidum; Chlorobi - chemistry; Chlorobi - cytology; Chlorobi - metabolism; Chlorobium tepidum; Chlorosome; Cyclopropane fatty acid; Cyclopropanes - chemistry; Cyclopropanes - metabolism; Fatty Acids - chemistry; Fatty Acids - metabolism; Glycolipid; glycolipids; Glycolipids - chemistry; Glycolipids - metabolism; photosynthetic bacteria; pigments; S-adenosylmethionine
• ISSN: 0968-0896; 1464-3391
• DOI: 10.1016/j.bmc.2013.04.030

Green photosynthetic bacteria have unique light-harvesting antenna systems called chlorosomes. Chlorobaculum tepidum, a model organism of the bacteria, biosynthesized monogalactosyl- and rhamnosylgalactosyldiacylglycerides possessing a methylene-bridged palmitoleyl group characterized by a cis-substituted cyclopropane ring as the dominant glycolipids of its chlorosome surface. The formation of the cyclopropane ring was chemically inhibited by supplementation of sinefungin, an analog of S-adenosyl-l-methionine, into the bacterial cultivation. The presence of the cyclopropane ring reinforced acid resistance of the light-harvesting chlorosomes and suppressed acidic demetalation (pheophytinization) of bacteriochlorophyll-c pigments constructing the core part of chlorosomes. The ring-formation would represent direct and post-synthetic modifications of chlorosome membrane properties and was tolerant of acidic environments.