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- Title
Isolation and characterization of a new bacteriochlorophyll- c bearing a neopentyl substituent at the 8-position from the bciD-deletion mutant of the brown-colored green sulfur bacterium Chlorobaculum limnaeum.
- Authors
Mizoguchi, Tadashi; Harada, Jiro; Tsukatani, Yusuke; Tamiaki, Hitoshi
- Abstract
We recently constructed the mutant of the brown-colored green sulfur bacterium Chlorobaculum limnaeum lacking BciD which was responsible for formation of a formyl group at the 7-position in bacteriochlorophyll(BChl)- e biosynthesis. This mutant exclusively gave BChl- c, but not BChl- e, as the chlorosome pigments (Harada et al. in PLoS One 8(4):e60026, ). By the mutation, the homolog and epimer composition of the pigment was drastically altered. The methylation at the 8-position in the mutant cells proceeded to create BChl- c carrying large alkyl substituents at this position. Correspondingly, the content of BChls- c having the ( S)-configuration at the chiral 3-position remarkably increased and accounted for 80.6 % of the total BChl- c. Based on the alteration of the pigment composition in the mutant cells, a new BChl- c bearing the bulkiest, triple 8-methylated neopentyl substituent at the 8-position ([N,E]BChl- c) was identified. The molecular structure of [N,E]BChl- c was fully determined by its NMR, mass, and circular dichroism spectra. The newly identified [N,E]BChl- c was epimerically pure at the chiral 3-position and its stereochemistry was determined to be an ( S)-configuration by modified Mosher's method. Further, the effects of the C8-methylation on the optical absorption properties of monomeric BChls- c were investigated. The Soret but not Qy absorption bands shifted to longer wavelengths by the extra methylation (at most 1.4 nm). The C8-methylation induced a slight but apparent effect on absorption properties of BChls- c in their monomeric states.
- Subjects
BACTERIOCHLOROPHYLLS; CHLOROBIACEAE; METHYLATION; MOLECULAR structure; NUCLEAR magnetic resonance; STEREOCHEMISTRY
- Publication
Photosynthesis Research, 2014, Vol 121, Issue 1, p3
- ISSN
0166-8595
- Publication type
Article
- DOI
10.1007/s11120-014-9977-8