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Spectral and photochemical properties of borohydride‐treated D1‐D2‐cytochrome b ‐559 complex of photosystem II
Author(s) -
Shkuropatov Anatoli Ya,
Khatypov Ravil A,
Volshchukova Tatyana S,
Shkuropatova Valentina A,
Owens Thomas G,
Shuvalov Vladimir A
Publication year - 1997
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/s0014-5793(97)01512-3
Subject(s) - photochemistry , borohydride , chemistry , photosystem ii , cytochrome b6f complex , cytochrome b , photosystem i , cytochrome , photosynthesis , biochemistry , catalysis , enzyme , mitochondrial dna , gene
The D1‐D2‐cytochrome b ‐559 reaction center complex of photosystem II with an altered pigment composition was prepared from the original complex by treatment with sodium borohydride (BH − 4 ). The absorption spectra of the modified and original complexes were compared to each other and to the spectra of purified chlorophyll a and pheophytin a (Pheo a ) treated with BH − 4 in methanolic solution. The results of these comparisons are consistent with the presence in the modified complex of an irreversibly reduced Pheo a molecule, most likely 13 1 ‐deoxo‐13 1 ‐hydroxy‐Pheo a , replacing one of the two native Pheo a molecules present in the original complex. Similar to the original preparation, the modified complex was capable of a steady‐state photoaccumulation of Pheo − and P680 + . It is concluded that the pheophytin a molecule which undergoes borohydride reduction is not involved in the primary charge separation and seems to represent a previously postulated photochemically inactive Pheo a molecule. The Q y and Q x transitions of this molecule were determined to be located at 5°C at 679.5–680 nm and 542 nm, respectively.