title: The 17-propionate esterifying variants of bacteriochlorophyll-a and bacteriopheophytin-a in purple photosynthetic bacteria.
abstract: Most purple photosynthetic bacteria contain bacteriochlorophyll(BChl)-a (a magnesium complex) and bacteriopheophytin(BPhe)-a (its free base) as their photoactive pigments. These pigments are composed of two parts: a cyclic tetrapyrrole as the chromophore and a long hydrocarbon-chain as the propionate-type esterifying group at the 17-position. The hydrocarbon-chain is usually an isoprenoid-type C20 phytyl (Phy) group in both the pigments. In the ester group of BChl-a, several variants such as geranylgeranyl (GG), dihydrogeranylgeranyl (DHGG) and tetrahydrogeranylgeranyl (THGG) groups were found in the final stage of BChl-a biosynthesis. On the other hand, the esterifying variants in BPhe-a have not been studied as much due to the lower levels of this pigment relative to BChl-a. The esterifying group does not affect the electronic absorption properties of such pigments in the monomeric state, but drastically alters the hydrophobicity. In this study, BChl-a and BPhe-a in the six phylogenetically distinct classes of purple bacteria were analyzed in terms of their esterifying groups in the 17-propionate residues, using high-performance liquid chromatography. Both BChls-a and BPhes-a carrying GG, DHGG and THGG in addition to the usual Phy were found for all the bacterial species studied at measurable levels. In some of the species, the ratio of BPhes-a esterified with GG, DHGG and THGG over the total BPhe-a drastically decreased in comparison with that of the corresponding BChls-a. Especially, the relative content of BPhe-a with GG largely decreased. This observation might indicate that BPhe-a as a cofactor of reaction centers was preferentially esterified with partially reduced and flexible chains (THGG and Phy) rather than less reduced and rigid ones (GG and DHGG).
authors.affiliation: Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Mizoguchi
authors.affiliation: Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
authors.forename: Megumi
authors.initials: M
authors.lastname: Isaji
authors.affiliation: Department of Medical Biochemistry, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan.
authors.forename: Jiro
authors.initials: J
authors.lastname: Harada
authors.affiliation: Earth-Life Science Institute, Tokyo Institute of Technology, Meguro, Tokyo 152-8550, Japan; PRESTO, Japan Science and Technology, Kawaguchi, Saitama 332-0012, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Tsukatani
authors.affiliation: Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan. Electronic address: tamiaki@fc.ritsumei.ac.jp.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tamiaki
mesh_terms: D025541:Bacteriochlorophyll A / Q000032:analysis / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D004951:Esterification; D057927:Hydrophobic and Hydrophilic Interactions; D010674:Pheophytins / Q000032:analysis / Q000737:chemistry*; D011422:Propionates / Q000737:chemistry*; D020560:Proteobacteria / Q000378:metabolism*; D013729:Terpenes / Q000737:chemistry
chemical_list: D025541:Bacteriochlorophyll A; D010674:Pheophytins; D011422:Propionates; D013729:Terpenes; C006678:bacteriopheophytin
keywords: Bacteriochlorophyll-a; Bacteriopheophytin-a; Geranylgeranyl reductase; High-performance liquid chromatography; Propionate-type ester group; Purple bacteria