Mutational analysis of the structure and biogenesis of the photosystem I reaction center in the cyanobacterium Synechocystis sp. PCC 6803

Journal Article · Mon Feb 01 00:00:00 EST 1993 · Proceedings of the National Academy of Sciences of the United States of America; (United States)

DOI:https://doi.org/10.1073/pnas.90.3.1132· OSTI ID:6826561

Smart, L B; McIntosh, L ^[1]; Warren, P V; Golbeck, J H ^[2]

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1. Michigan State Univ., East Lansing (United States)
2. 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

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
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