Mutational analysis of the structure and biogenesis of the photosystem I reaction center in the cyanobacterium Synechocystis sp. PCC 6803
- Michigan State Univ., East Lansing (United States)
- Univ. of Nebraska, Lincoln (United States)
The authors have utilized the unicellular cyanobacterium Synechocystis sp. PCC 6803 to incorporate site-directed amino acid substitutions into the photosystem I (PSI) reaction-center protein PsaB. A cysteine residue (position 565 of PSaB) proposed to serve as a ligand to the [4Fe-4S] center F[sub x] was changed to serine, histidine, and aspartate. These three mutants - C565S, C565H, and C565D - all exhibited greatly reduced accumulation of PSI reaction-center proteins and failed to grow autotrophically, indicating that this cysteine most likely does coordinate F[sub x], which is crucial for PSI biogenesis. Interestingly, the strain C565S accumulated significantly more PSI than the other two cysteine mutants and displayed photoreduction of the [4Fe-4S] terminal electron acceptors F[sub A] and F[sub B]. Mutations were also introduced into a leucine zipper motif of PsaB, proposed to participate in reaction-center dimerization. The mutants L522V, L536M, and L522V/L536M all exhibited wild-type characteristics and grew autotrophically, whereas the L522P mutation prevented PSI accumulation. These data do not provide support for a major structural role of the leucine zipper in reaction-center dimerization or in assembly of F[sub x]. However, the amino acid substitutions incorporated were conservative and might not have perturbed the leucine zipper. 31 refs., 4 figs., 1 tab.
- OSTI ID:
- 6826561
- Journal Information:
- Proceedings of the National Academy of Sciences of the United States of America; (United States), Vol. 90:3; ISSN 0027-8424
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
AMINO ACIDS
BIOSYNTHESIS
BACTERIA
MUTATIONS
BIOCHEMISTRY
DIMERIZATION
GROWTH
MOLECULAR STRUCTURE
PHOTOSYNTHESIS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CHEMISTRY
MICROORGANISMS
ORGANIC ACIDS
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
POLYMERIZATION
SYNTHESIS
550200* - Biochemistry