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  • XVI.A.2.c. PSI-F
  • Sequences of PSI-F
  • Sequence Similarity Search for PSI-F

    XVI.A.2.c. PSI-F

    The mature PSI-F polypeptide from spinach has a molecular weight of about 17 kDa (for a general review see Andersen and Scheller, 1993). It is rich in charged amino acids. The transmembrane helical profile of the spinach polypeptide suggests the presence of two membrane-spanning helices (Rebeiz, unpublished). PSI-F appears to be an extrinsic protein. In barley it is often lost during purification of PSI and is extrqactable with n-butanol. In spinach the PSI-F polypeptide partinons into Triton X- 114 micelles.

    Transit peptides of the PSI-F precursor contain a hydrophobic region typical of transit peptides targeted to the thylakoid lumen. It is believed that subunit III of PSI-F plays a role in facilitating electron donation from plastocyanin to the reaction center P700. Since PSI-F contains a surplus of basic amino acid residues, it may enable negatively charged plastocyanin to react with PSI in a manner similar to the proposed function of PSI-D in the binding of ferredoxin.

    A query for psaF addressed to the various protein databases listed in the Biology Workbench, yielded 33 records which are depicted under Sequenced PSI-F. These sequences can be used for Sequence Similarity Searches or other manipulations using one of several routines described in the Biology Workbench or elsewhere (see AntheproW which can be downloaded via anonymous ftp from: ibcp.fr; pub/Antheprot/Windows/anthe 3_1 directory). For example a Blast Sequence Similarity Search of spinach PSI-F addressed to the Biology Workbench (SwissProt database) is depicted below.

    Sequences of PSI-F

    Click on Sequences to view the sequences of PSI-F retrieved from various protein sequence databases by the Biology Workbench.

    Sequence Similarity Search for PSI-F

    Click on Sequence Similarity Search to view the Blast sequence similarity search results of barley PSI-F from the Biology workbench (SwissProt database).

    References

    1. Andersen, B. and H. V. Scheller (1993). Structure, Function and Assembly of photosystem I. In: Pigment-Protein Complexes In Plastids: Synthesis and Assembly . C. Sundqvist and M. Ryberg, (eds.), p 383-417, Academic Press, New York.

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