Amino acid deletions in loop C of the chlorophyll a-binding protein CP47 alter the chloride requirement and/or prevent the assembly of photosystemII

Amino acid deletions in loop C of the chlorophyll a-binding protein CP47 alter the chloride... The chlorophyll a-binding protein CP47 directs excitation energy to the reaction center of photosystem II (PSII) during oxygenic photosynthesis and has additional structural and functional roles associated with the PSII water-oxidizing complex. Oligonucleotide-directed mutagenesis was employed to study loop C of CP47 (approximately Trp-162 to Gly-197) which faces the thylakoid lumen. Five short amino acid deletion strains, Δ(S169–P171), Δ(Y172–G176), Δ(G176–P180), Δ(E184–A188) and Δ(F190–N194), were created that span this domain. The deletion between Gly-176 and Pro-180, located around the middle of loop C, produced an obligate photoheterotroph that could not assemble functional PSII centers. The deletions in mutants Δ(S169–P171) and Δ(Y172–G176) reduced PSII levels to ≤ 20% of the control and thus impaired photoautotrophic growth. In contrast, mutants Δ(E184-A188) and Δ(F190–N194) were photoautotrophic even though the number of photosystems was decreased by 50%. All PSII complexes assembled in the deletion strains had an increased susceptibility to photoinactivation and deletion of Glu-184 to Ala-188 prevented photoautotrophic growth under chloride-limiting conditions. Furthermore, the removal of the extrinsic PSII-O, PSII-U and PSII-V proteins from mutants Δ(E184–A188) and Δ(F190–N194) reduced the rates of oxygen evolution and, in the strains lacking either the PSII-O or PSII-V proteins, also increased the photoautotrophic doubling times. These effects were greater in mutant Δ(E184–A188) than in mutant Δ(F190–N194) and the order of importance for the removal of the extrinsic proteins was found to be ΔPSII-V ≥ ΔPSII-O > ΔPSII-U. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Molecular Biology Springer Journals

Amino acid deletions in loop C of the chlorophyll a-binding protein CP47 alter the chloride requirement and/or prevent the assembly of photosystemII

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Publisher
Kluwer Academic Publishers
Copyright
Copyright © 2000 by Kluwer Academic Publishers
Subject
Life Sciences; Biochemistry, general; Plant Sciences; Plant Pathology
ISSN
0167-4412
eISSN
1573-5028
D.O.I.
10.1023/A:1026528813583
Publisher site
See Article on Publisher Site

Abstract

The chlorophyll a-binding protein CP47 directs excitation energy to the reaction center of photosystem II (PSII) during oxygenic photosynthesis and has additional structural and functional roles associated with the PSII water-oxidizing complex. Oligonucleotide-directed mutagenesis was employed to study loop C of CP47 (approximately Trp-162 to Gly-197) which faces the thylakoid lumen. Five short amino acid deletion strains, Δ(S169–P171), Δ(Y172–G176), Δ(G176–P180), Δ(E184–A188) and Δ(F190–N194), were created that span this domain. The deletion between Gly-176 and Pro-180, located around the middle of loop C, produced an obligate photoheterotroph that could not assemble functional PSII centers. The deletions in mutants Δ(S169–P171) and Δ(Y172–G176) reduced PSII levels to ≤ 20% of the control and thus impaired photoautotrophic growth. In contrast, mutants Δ(E184-A188) and Δ(F190–N194) were photoautotrophic even though the number of photosystems was decreased by 50%. All PSII complexes assembled in the deletion strains had an increased susceptibility to photoinactivation and deletion of Glu-184 to Ala-188 prevented photoautotrophic growth under chloride-limiting conditions. Furthermore, the removal of the extrinsic PSII-O, PSII-U and PSII-V proteins from mutants Δ(E184–A188) and Δ(F190–N194) reduced the rates of oxygen evolution and, in the strains lacking either the PSII-O or PSII-V proteins, also increased the photoautotrophic doubling times. These effects were greater in mutant Δ(E184–A188) than in mutant Δ(F190–N194) and the order of importance for the removal of the extrinsic proteins was found to be ΔPSII-V ≥ ΔPSII-O > ΔPSII-U.

Journal

Plant Molecular BiologySpringer Journals

Published: Oct 16, 2004

References

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