title: Biosynthesis of unnatural bacteriochlorophyll c derivatives esterified with α,ω-diols in the green sulfur photosynthetic bacterium Chlorobaculum tepidum.
abstract: Unnatural bacteriochlorophyll (BChl) c derivatives possessing a hydroxy group at the terminus of a hydrocarbon chain at the 17-propionate were biosynthesized in the green sulfur photosynthetic bacterium Chlorobaculum tepidum. Addition of exogenous 1,8-octanediol, 1,12-dodecanediol, and 1,16-hexadecanediol in acetone to liquid cultures resulted in accumulation of BChl c monoesterified with the corresponding diols. The relative ratios of the novel BChl c derivatives esterified with 1,8-, 1,12-, and 1,16-diols to totally producing BChl c were 8.2, 50.2, and 57.6% in the cells grown with additive α,ω-diols at concentrations of 1.5, 0.06, and 0.06 mM, respectively, at the final concentration. The homologue composition of BChl c derivatives esterified with these α,ω-diols was similar to that of original, coexisting BChl c esterified with farnesol (BChl c(F)), suggesting that esterification of α,ω-diols occurred at the last step of the BChl c biosynthetic pathway by BChl c synthase, BchK, in the same manner as in BChl c(F). Chlorosomes, which were isolated from cells grown in the presence of exogenous α,ω-diols, contained a ratio and a composition of BChl c derivatives esterified with the diols similar to those in the whole cells, indicating that these BChl c derivatives were actually present in chlorosomes. Q(y) absorption bands of C. tepidum cells containing the novel BChl c derivatives were shifted to a shorter wavelength, although their bandwidths were analogous to those of cells obtained by normal cultivation. Circular dichroism spectra of cells that had BChl c derivatives esterified with α,ω-diols exhibited S-shaped signals in the Q(y) region, whose polarities were the reverse of those of cells grown in the normal medium and by supplementation with neat acetone as a control experiment. These spectral features of C. tepidum possessing BChl c derivatives esterified with α,ω-diols imply that the novel BChl c derivatives possessing a hydroxy group at the terminus of a hydrocarbon chain affect their self-assembly in chlorosomes.
authors.affiliation: Department of Chemistry, Faculty of Science and Engineering, Kinki University, Higashi-Osaka, Osaka 577-8502, Japan.
authors.forename: Risato
authors.initials: R
authors.lastname: Nishimori
authors.forename: Tadashi
authors.initials: T
authors.lastname: Mizoguchi
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tamiaki
authors.forename: Shigenori
authors.initials: S
authors.lastname: Kashimura
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Saga
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis*; D001429:Bacteriochlorophylls / Q000096:biosynthesis*; D019414:Chlorobi / Q000378:metabolism*; D002942:Circular Dichroism; D005204:Farnesol / Q000737:chemistry / Q000378:metabolism; D010788:Photosynthesis; D013455:Sulfur / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D005204:Farnesol; C002084:bacteriochlorophyll c; D013455:Sulfur