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Polypeptide composition of higher plant photosystem I complex
Author(s) -
Ikeuchi Masahiko,
Hirano Atsushi,
Hiyama Tetsuo,
Inoue Yorinao
Publication year - 1990
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(90)81391-z
Subject(s) - spinach , photosystem i , photosystem ii , biology , molecular mass , chloroplast , protein subunit , biochemistry , chlorophyll , photosystem , photosynthesis , gene , botany , enzyme
High resolution gel electrophoresis of the native photosystem I complex retaining light‐harvesting chlorophyll complex revealed the presence of three low‐molecular‐mass proteins of 7, 4.1 and 3.9 kDa in spinach, and 6.8, 4.4 and 4.1 kDa in pea, in addition to the other well‐characterized higher‐molecular‐mass components. Upon further detergent treatment to deplete light‐harvesting chlorophyll complex, the 7 kDa and 4.1 kDa proteins were removed from the photosystem I core complex of spinach, while the 3.9 kDa protein was retained. N‐terminal sequencing demonstrated that the 4.1 kDa proteins from both spinach and pea correspond to the gene product of ORF42/44 in chloroplast genome of liverwort and higher plants, which was previously hypothesized as a photosystem I gene ( psa J) based on sequence homology with the cyanobacterial photosystem I component of 4.1 kDa [(1989) FEBS Lett. 253, 257‐263]. N‐terminal sequence of the spinach 3.9 kDa and pea 4.4 kDa proteins fitted with chloroplast ORF36/40 ( psa I) although no homologue has been found in cyanobacteria. The spinach 7 kDa and pea 6.8 kDa proteins correspond to the nuclear‐encoded psa K product and significantly matched with the N‐terminal sequence of the cyanobacterial 6.5 kDa subunit. The evolutional conservation of the psa J and psa K seems to suggest their intrinsic role(s) in photosystem I.