Molecular genetic analysis of terminal steps in bacteriochlorophyll a biosynthesis

Characterization of a Rhodobacter capsulatus strain that synthesizes geranylgeraniol-esterified bacteriochlorophyll a

D. W. Bollivar, S. Wang, James Paul Allen, C. E. Bauer

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Abstract

Site-directed mutational analysis of the Rhodobacter capsulatus photosynthesis gene cluster was undertaken in order to identify and characterize genetic loci involved in bacteriochlorophyll a biosynthesis. A mutant in orf304 was shown to accumulate the tetrapyrrole intermediate 'bacteriochlorophyllide a' which is a tetrapyrrole that has a bacteriochlorophyll a ring structure without the presence of an esterifying alcohol. A mutant in orf391 is shown to synthesize bacteriochlorophyll a that is esterified with geranylgeraniol rather than the normal phytol. This latter result provides the first genetic confirmation that esterification of bacteriochlorophyllide a initially involves the addition of a geranylgeraniol group followed by sequential reduction of the geranylgeraniol moiety to phytol which is the end product of the pathway. An R. capsulatus strain synthesizing geranylgeraniol-esterified bacteriochlorophyll is shown to exhibit severely impaired photosynthetic growth capability. This is despite our observation that synthesis of geranylgeraniol-esterified bacteriochlorophyll does not affect the energy transfer rate from light harvesting to reaction center complexes nor the electron transfer function as measured by the yield of electron transfer to the primary and secondary quinones, the charge recombination rate from the quinones, and the rate of cytochrome c2 oxidation. We conclude that the observed reduction of the photosynthetic growth rate observed for R. capsulatus strains that synthesize geranylgeraniol-esterified bacteriochlorophyll is primarily a consequence of the reduced steady-state level of the photosystem.

Original languageEnglish
Pages (from-to)12763-12768
Number of pages6
JournalBiochemistry
Volume33
Issue number43
DOIs
Publication statusPublished - 1994

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Rhodobacter capsulatus
Bacteriochlorophylls
Biosynthesis
Molecular Biology
Phytol
Tetrapyrroles
Quinones
Cytochromes c2
Electrons
Genetic Loci
Photosynthesis
Esterification
Energy Transfer
Multigene Family
Growth
Energy transfer
Genetic Recombination
Transfer functions
geranylgeraniol
Genes

ASJC Scopus subject areas

  • Biochemistry

Cite this

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title = "Molecular genetic analysis of terminal steps in bacteriochlorophyll a biosynthesis: Characterization of a Rhodobacter capsulatus strain that synthesizes geranylgeraniol-esterified bacteriochlorophyll a",
abstract = "Site-directed mutational analysis of the Rhodobacter capsulatus photosynthesis gene cluster was undertaken in order to identify and characterize genetic loci involved in bacteriochlorophyll a biosynthesis. A mutant in orf304 was shown to accumulate the tetrapyrrole intermediate 'bacteriochlorophyllide a' which is a tetrapyrrole that has a bacteriochlorophyll a ring structure without the presence of an esterifying alcohol. A mutant in orf391 is shown to synthesize bacteriochlorophyll a that is esterified with geranylgeraniol rather than the normal phytol. This latter result provides the first genetic confirmation that esterification of bacteriochlorophyllide a initially involves the addition of a geranylgeraniol group followed by sequential reduction of the geranylgeraniol moiety to phytol which is the end product of the pathway. An R. capsulatus strain synthesizing geranylgeraniol-esterified bacteriochlorophyll is shown to exhibit severely impaired photosynthetic growth capability. This is despite our observation that synthesis of geranylgeraniol-esterified bacteriochlorophyll does not affect the energy transfer rate from light harvesting to reaction center complexes nor the electron transfer function as measured by the yield of electron transfer to the primary and secondary quinones, the charge recombination rate from the quinones, and the rate of cytochrome c2 oxidation. We conclude that the observed reduction of the photosynthetic growth rate observed for R. capsulatus strains that synthesize geranylgeraniol-esterified bacteriochlorophyll is primarily a consequence of the reduced steady-state level of the photosystem.",
author = "Bollivar, {D. W.} and S. Wang and Allen, {James Paul} and Bauer, {C. E.}",
year = "1994",
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T1 - Molecular genetic analysis of terminal steps in bacteriochlorophyll a biosynthesis

T2 - Characterization of a Rhodobacter capsulatus strain that synthesizes geranylgeraniol-esterified bacteriochlorophyll a

AU - Bollivar, D. W.

AU - Wang, S.

AU - Allen, James Paul

AU - Bauer, C. E.

PY - 1994

Y1 - 1994

N2 - Site-directed mutational analysis of the Rhodobacter capsulatus photosynthesis gene cluster was undertaken in order to identify and characterize genetic loci involved in bacteriochlorophyll a biosynthesis. A mutant in orf304 was shown to accumulate the tetrapyrrole intermediate 'bacteriochlorophyllide a' which is a tetrapyrrole that has a bacteriochlorophyll a ring structure without the presence of an esterifying alcohol. A mutant in orf391 is shown to synthesize bacteriochlorophyll a that is esterified with geranylgeraniol rather than the normal phytol. This latter result provides the first genetic confirmation that esterification of bacteriochlorophyllide a initially involves the addition of a geranylgeraniol group followed by sequential reduction of the geranylgeraniol moiety to phytol which is the end product of the pathway. An R. capsulatus strain synthesizing geranylgeraniol-esterified bacteriochlorophyll is shown to exhibit severely impaired photosynthetic growth capability. This is despite our observation that synthesis of geranylgeraniol-esterified bacteriochlorophyll does not affect the energy transfer rate from light harvesting to reaction center complexes nor the electron transfer function as measured by the yield of electron transfer to the primary and secondary quinones, the charge recombination rate from the quinones, and the rate of cytochrome c2 oxidation. We conclude that the observed reduction of the photosynthetic growth rate observed for R. capsulatus strains that synthesize geranylgeraniol-esterified bacteriochlorophyll is primarily a consequence of the reduced steady-state level of the photosystem.

AB - Site-directed mutational analysis of the Rhodobacter capsulatus photosynthesis gene cluster was undertaken in order to identify and characterize genetic loci involved in bacteriochlorophyll a biosynthesis. A mutant in orf304 was shown to accumulate the tetrapyrrole intermediate 'bacteriochlorophyllide a' which is a tetrapyrrole that has a bacteriochlorophyll a ring structure without the presence of an esterifying alcohol. A mutant in orf391 is shown to synthesize bacteriochlorophyll a that is esterified with geranylgeraniol rather than the normal phytol. This latter result provides the first genetic confirmation that esterification of bacteriochlorophyllide a initially involves the addition of a geranylgeraniol group followed by sequential reduction of the geranylgeraniol moiety to phytol which is the end product of the pathway. An R. capsulatus strain synthesizing geranylgeraniol-esterified bacteriochlorophyll is shown to exhibit severely impaired photosynthetic growth capability. This is despite our observation that synthesis of geranylgeraniol-esterified bacteriochlorophyll does not affect the energy transfer rate from light harvesting to reaction center complexes nor the electron transfer function as measured by the yield of electron transfer to the primary and secondary quinones, the charge recombination rate from the quinones, and the rate of cytochrome c2 oxidation. We conclude that the observed reduction of the photosynthetic growth rate observed for R. capsulatus strains that synthesize geranylgeraniol-esterified bacteriochlorophyll is primarily a consequence of the reduced steady-state level of the photosystem.

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