{PDOC00786}
{PS01026; PHOTOSYSTEM_I_PSAGK}
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* Photosystem I psaG and psaK proteins signature *
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Photosystem I  (PSI)  [1]  is  an integral membrane protein complex  that uses
light energy to mediate electron transfer from plastocyanin to ferredoxin.  It
is found  in  the chloroplasts of plants and cyanobacteria. PSI is composed of
at least  14  different  subunits,  two of which - PSI-G (gene psaG) and PSI-K
(gene psaK)  -  are  small  hydrophobic  proteins  of  about  7  to  9  Kd and
evolutionary related  [2].  Both  seem  to  contain two transmembrane regions.
Cyanobacteria seem to encode only for PSI-K.

As a signature  pattern, we selected the best  conserved region which seems to
correspond to the second transmembrane region.

-Consensus pattern: [GTND]-[FPMI]-x-[LIVMH]-x-[DEAT]-x(2)-[GA]-x-[GTAM]-[STA]-
                    x-G-H-x-[LIVM]-[GAS]
-Sequences known to belong to this class detected by the pattern: ALL,  except
 for Cyanidium caldarium psaK.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: December 2004 / Pattern and text revised.

[ 1] Golbeck J.H.
     "Structure, function and organization of the Photosystem I reaction
     center complex."
     Biochim. Biophys. Acta 895:167-204(1987).
     PubMed=3333014
[ 2] Kjaerulff S., Andersen B., Nielsen V.S., Moller B.L., Okkels J.S.
     "The PSI-K subunit of photosystem I from barley (Hordeum vulgare L.).
     Evidence for a gene duplication of an ancestral PSI-G/K gene."
     J. Biol. Chem. 268:18912-18916(1993).
     PubMed=8360180

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