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PHOTOREVERSIBLE Ca2+‐DEPENDENT AGGREGATION OF PURIFIED PHYTOCHROME FROM ETIOLATED PEA AND RYE SEEDLINGS
Author(s) -
Yamamoto Kotaro T.,
Jr William O. Smith,
Furuya Masaki
Publication year - 1980
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1980.tb04014.x
Subject(s) - phytochrome , etiolation , pisum , secale , biology , turbidimetry , centrifugation , botany , phytochrome a , biophysics , biochemistry , chemistry , red light , enzyme , arabidopsis , gene , mutant
— The aggregation of phytochrome purified from etiolated pea ( Pisum satirum cv. Alaska) and rye ( Secale cereale cv. Cougar) tissues was investigated by centrifugation and turbidimetry. Purified pea phytochrome (A 669 /A 280 = 0.88), if irradiated with red light, became precipitable in the presence of CaCl 2 . The precipitation upon red‐light irradiation was optimal at a Ca 2‐ or Mg 2+ concentration of 10–20 m M , was greater at increased phytochrome concentration or lower pH values, and was inhibited by 0.1 M KG. The precipitated phytochrome slowly became soluble after far‐red light exposure. Turbidity of pea phytochrome solutions after red‐light irradiation also increased rapidly in the presence of either Ca 2+ or Mg 2+ . Far‐red light exposure after the red light cancelled the turbidity increase. Rye phytochrome showed less turbidity increase than pea phytochrome and occurred only in the presence of Ca 2+ . Partially degraded pea phytochrome produced by endogenous proteases in the extract did not show the turbidity increase. Undegraded pea phytochrome also associated with microsomal fractions under conditions similar to those described above, but the partially degraded phytochrome did not.