Skip to main content
Plant Physiology logoLink to Plant Physiology
. 1995 Jul;108(3):1067–1075. doi: 10.1104/pp.108.3.1067

Organization of photosystem I polypeptides. Identification of PsaB domains that may interact with PsaD.

Q Xu 1, P R Chitnis 1
PMCID: PMC157458  PMID: 7630936

Abstract

PsaA and PsaB are homologous integral membrane-proteins that form the heterodimeric core of photosystem i (PSI). We used subunit-deficient PSI complexes from the mutant strains of the cyanobacterium Synechocystis sp. PCC 6803 to examine interactions between PsaB and other PSI subunits. Incubation of the wild-type PSI with thermolysin yielded 22-kD C-terminal fragments of PsaB that were resistant to further proteolysis. Modification of the wild-type PSI with N-hydroxysuccinimidobiotin and subsequent cleavage by thermolysin showed that the lysyl residues in the 22-kD C-terminal domain were inaccessible to modification by N-hydroxysuccinimidobiotin. The absence of PsaE, PsaF, PsaI, PsaJ, or PsaL facilitated accumulation of 22-kD C-terminal fragments of PsaB but did not alter their resistance to further proteolysis. When the PsaD-less PSI was treated with thermolysin, the 22-kD C-terminal fragments of PsaB were rapidly cleaved, with concomitant accumulation of a 16-kD fragment and then a 3.4-kD one. We mapped the N termini of these fragments by N-terminal amino acid sequencing and the C termini from their positive reaction with an antibody against the C-terminal peptide of PsaB. The cleavage sites were proposed to be in the extramembrane loops on the cytoplasmic side. Western blot analyses showed resistance of PsaC and PsaI to proteolysis prior to cleavage of the 22-kD fragments. Therefore, we propose that PsaD shields two extramembrane loops of PsaB and protects the C-terminal domain of PsaB from in vitro proteolysis.

Full Text

The Full Text of this article is available as a PDF (2.7 MB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Arnon D. I. COPPER ENZYMES IN ISOLATED CHLOROPLASTS. POLYPHENOLOXIDASE IN BETA VULGARIS. Plant Physiol. 1949 Jan;24(1):1–15. doi: 10.1104/pp.24.1.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Bayer E. A., Wilchek M. Protein biotinylation. Methods Enzymol. 1990;184:138–160. doi: 10.1016/0076-6879(90)84268-l. [DOI] [PubMed] [Google Scholar]
  3. Chitnis P. R., Nelson N. Assembly of Two Subunits of the Cyanobacterial Photosystem I on the n-Side of Thylakoid Membranes. Plant Physiol. 1992 May;99(1):239–246. doi: 10.1104/pp.99.1.239. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Chitnis P. R., Purvis D., Nelson N. Molecular cloning and targeted mutagenesis of the gene psaF encoding subunit III of photosystem I from the cyanobacterium Synechocystis sp. PCC 6803. J Biol Chem. 1991 Oct 25;266(30):20146–20151. [PubMed] [Google Scholar]
  5. Chitnis P. R., Reilly P. A., Miedel M. C., Nelson N. Structure and targeted mutagenesis of the gene encoding 8-kDa subunit of photosystem I from the cyanobacterium Synechocystis sp. PCC 6803. J Biol Chem. 1989 Nov 5;264(31):18374–18380. [PubMed] [Google Scholar]
  6. Chitnis V. P., Chitnis P. R. PsaL subunit is required for the formation of photosystem I trimers in the cyanobacterium Synechocystis sp. PCC 6803. FEBS Lett. 1993 Dec 27;336(2):330–334. doi: 10.1016/0014-5793(93)80831-e. [DOI] [PubMed] [Google Scholar]
  7. Chitnis V. P., Xu Q., Yu L., Golbeck J. H., Nakamoto H., Xie D. L., Chitnis P. R. Targeted inactivation of the gene psaL encoding a subunit of photosystem I of the cyanobacterium Synechocystis sp. PCC 6803. J Biol Chem. 1993 Jun 5;268(16):11678–11684. [PubMed] [Google Scholar]
  8. Cohen Y., Chitnis V. P., Nechushtai R., Chitnis P. R. Stable assembly of PsaE into cyanobacterial photosynthetic membranes is dependent on the presence of other accessory subunits of photosystem I. Plant Mol Biol. 1993 Nov;23(4):895–900. doi: 10.1007/BF00021544. [DOI] [PubMed] [Google Scholar]
  9. Fish L. E., Bogorad L. Identification and analysis of the maize P700 chlorophyll a apoproteins PSI-A1 and PSI-A2 by high pressure liquid chromatography analysis and partial sequence determination. J Biol Chem. 1986 Jun 25;261(18):8134–8139. [PubMed] [Google Scholar]
  10. Frankel L. K., Bricker T. M. Interaction of CPa-1 with the manganese-stabilizing protein of photosystem II: identification of domains on CPa-1 which are shielded from N-hydroxysuccinimide biotinylation by the manganese-stabilizing protein. Biochemistry. 1992 Nov 17;31(45):11059–11064. doi: 10.1021/bi00160a015. [DOI] [PubMed] [Google Scholar]
  11. Golbeck J. H. Shared thematic elements in photochemical reaction centers. Proc Natl Acad Sci U S A. 1993 Mar 1;90(5):1642–1646. doi: 10.1073/pnas.90.5.1642. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Henry R. L., Takemoto L. J., Murphy J., Gallegos G. L., Guikema J. A. Development and use of domain-specific antibodies in a characterization of the large subunits of soybean photosystem 1. Plant Physiol Biochem. 1992;30(3):357–364. [PubMed] [Google Scholar]
  13. Kuhn M., Fromme P., Krabben L. A 'membrane attached' alpha-helix: a conserved structural motif in bacterial reaction centres, photosystem I and chloroplast NADH-plastoquinone oxidoreductase. Trends Biochem Sci. 1994 Oct;19(10):401–402. doi: 10.1016/0968-0004(94)90085-x. [DOI] [PubMed] [Google Scholar]
  14. Lagoutte B., Vallon O. Purification and membrane topology of PSI-D and PSI-E, two subunits of the photosystem I reaction center. Eur J Biochem. 1992 May 1;205(3):1175–1185. doi: 10.1111/j.1432-1033.1992.tb16888.x. [DOI] [PubMed] [Google Scholar]
  15. Li N., Zhao J. D., Warren P. V., Warden J. T., Bryant D. A., Golbeck J. H. PsaD is required for the stable binding of PsaC to the photosystem I core protein of Synechococcus sp. PCC 6301. Biochemistry. 1991 Aug 6;30(31):7863–7872. doi: 10.1021/bi00245a028. [DOI] [PubMed] [Google Scholar]
  16. Reilly P., Hulmes J. D., Pan Y. C., Nelson N. Molecular cloning and sequencing of the psaD gene encoding subunit II of photosystem I from the cyanobacterium, Synechocystis sp. PCC 6803. J Biol Chem. 1988 Nov 25;263(33):17658–17662. [PubMed] [Google Scholar]
  17. Smart L. B., McIntosh L. Expression of photosynthesis genes in the cyanobacterium Synechocystis sp. PCC 6803: psaA-psaB and psbA transcripts accumulate in dark-grown cells. Plant Mol Biol. 1991 Nov;17(5):959–971. doi: 10.1007/BF00037136. [DOI] [PubMed] [Google Scholar]
  18. Smart L. B., Warren P. V., Golbeck J. H., McIntosh L. Mutational analysis of the structure and biogenesis of the photosystem I reaction center in the cyanobacterium Synechocystis sp. PCC 6803. Proc Natl Acad Sci U S A. 1993 Feb 1;90(3):1132–1136. doi: 10.1073/pnas.90.3.1132. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Vallon O., Bogorad L. Topological study of PSI-A and PSI-B, the large subunits of the photosystem-I reaction center. Eur J Biochem. 1993 Jun 15;214(3):907–915. doi: 10.1111/j.1432-1033.1993.tb17994.x. [DOI] [PubMed] [Google Scholar]
  20. Vermaas W. F. Evolution of heliobacteria: implications for photosynthetic reaction center complexes. Photosynth Res. 1994;41:285–294. [PubMed] [Google Scholar]
  21. Xu Q., Armbrust T. S., Guikema J. A., Chitnis P. R. Organization of Photosystem I Polypeptides (A Structural Interaction between the PsaD and PsaL Subunits). Plant Physiol. 1994 Nov;106(3):1057–1063. doi: 10.1104/pp.106.3.1057. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Xu Q., Jung Y. S., Chitnis V. P., Guikema J. A., Golbeck J. H., Chitnis P. R. Mutational analysis of photosystem I polypeptides in Synechocystis sp. PCC 6803. Subunit requirements for reduction of NADP+ mediated by ferredoxin and flavodoxin. J Biol Chem. 1994 Aug 26;269(34):21512–21518. [PubMed] [Google Scholar]
  23. Xu Q., Yu L., Chitnis V. P., Chitnis P. R. Function and organization of photosystem I in a cyanobacterial mutant strain that lacks PsaF and PsaJ subunits. J Biol Chem. 1994 Feb 4;269(5):3205–3211. [PubMed] [Google Scholar]
  24. Zilber A. L., Malkin R. Organization and topology of photosystem I subunits. Plant Physiol. 1992 Jul;99(3):901–911. doi: 10.1104/pp.99.3.901. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Plant Physiology are provided here courtesy of Oxford University Press

RESOURCES