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GrainGenes Reference Report: PMB-18-989

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Reference	PMB-18-989
Title	A cDNA clone from barley encoding the precursor from the photosystem I polypeptide PSI-G sequence similarity to PSI-K
Journal	Plant Molecular Biology
Year	1992
Volume	18
Pages	989-994
Author	Okkels JS Nielsen VS Scheller HV Moller BL
Abstract	A cDNA clone encoding the photosystem I subunit, PSI-G was isolated from barley [Hordeum vulgare] using an oligonucleotide specifying a partial amino acid sequence from a 9 kDa polypeptide of barley photosystem I. The 724 bp sequence contains an open reading frame encoding a precursor polypeptide of 15 107 kDa. Import studies using the in vitro expressed barley PsaG cDNA clone demonstrate that PSI-G migrates with an apparent molecular mass of 9 kDa on SDS- polyacrylamide gels together with PSI-C (subunit-VII). The previous assignment of the gene product of PsaG from spinach as subunit V (Steppuhn J, Hermans J, Nechushtai R, Ljungberg U, Thuemmler F, Lottspeich F, Herrmann RG, FEBS Lett 237: 218-224, 1988) needs to be re-examined. The expression of the psaG gene is light-induced similar to other barley photosystem I genes. A significant sequence similarity to PSI-K from Chlamydomonas reinhardtii was discovered when a gene database was searched with the barley PSI-G amino acid sequence. Extensive sequence similarity between the nuclear-encoded photosystem I subunits has not previously been found. The observed sequence similarity between PSI-G and PSI-K suggests in symmetric location of these subunits in the photosystem I complex. The hydropathy plot of the barley PSI-G polypeptide indicates two membrane-spanning regions which are also found at the corresponding locations in the PSI-K polypeptide. PSI-G and PSI-K probably have evolved from a gene duplication of an ancestral gene.
Probe	PsaG
Keyword	Amino acid sequence [ Show all 9 ]

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