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  • XVI.A.2.e. PSI-H
  • Sequences of PSI-H
  • Sequence Similarity Search for PSI-H

    XVI.A.2.e. PSI-H

    The primary structure of the PSI-H polypeptide is known from sequences of cDNA clones of barley, spinach, and C. reinhardtii (for a general review see Andersen and Scheller, 1993). This polypeptide has not been found in cyanobacteria. In barley, it has an apparent molecular mass of 9.53 kDa and a calculated molecular mass of 10.24 kDa.

    The PSI-H polypeptide consists of a membrane spanning hydrophobic domain sandwiched between a very hydrophilic and highly conserved N-terminal domain which protrudes in the stroma, and a second hydrophilic domain. The hydrophobic domain is not conserved. This pattern is opposite to that of PSI-G and K, where the membrane spanning hydrophobic segments are highly conserved and the hydrophilic ones are not.

    PSI-H may act as an anchor for the PSI-D polypeptide. It has been suggested that the PSI-H polypeptide and the N-terminal domains of PSI-D and PSI-E may constitute a system for binding the peripheral polypeptides of the PSI complex in plants. It has also been suggested that it may bind the LHCI polypeptides.

    A query for psaH addressed to the various protein databases listed in the Biology Workbench, yielded 21 records which are depicted under Sequenced PSI-H. 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 barley PSI-H addressed to the Biology Workbench (SwissProt database) is depicted below.

    Sequences of PSI-H

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

    Sequence Similarity Search for PSI-H

    Click on Sequence Similarity Search to view the Blast sequence similarity search results of barley PSI-H 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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