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Orientation of the chromophore transition moment in the 4‐leaved shape model for pea phytochrome molecule in the red‐light absorbing form and its rotation induced by the phototransformation to the far‐red‐light absorbing form
Author(s) -
Tokutomi Satoru,
Mimuro Mamoru
Publication year - 1989
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(89)81119-6
Subject(s) - phytochrome , chromophore , circular dichroism , linear dichroism , chemistry , dichroism , transition dipole moment , molecule , crystallography , rotation (mathematics) , photochemistry , physics , optics , biology , red light , botany , organic chemistry , geometry , mathematics
Orientation of the chromophore transition moment in pea phytochrome (subunit molecular mass, 114 kDa) in the red‐light‐absorbing form (P r ) and its rotation induced by the phototransformation to the far‐red‐light‐absorbing (P fr ) form was studied by measuring linear dichroism of oriented phytochrome prepared by a ‘gel squeezing method’. The phytochrome in P r showed a negative linear dichroism. On the contrary, the P fr form showed positive linear dichroism. Assuming that the molecular axis for the two‐fold rotational symmetry in the ‘4‐leaved shape model’ proposed recently for the dimeric molecular structure of the phytochrome [(1989) FEBS Lett. 247, 139–142], is oriented in parallel with the direction of the external constraint, the average azimuthal angle between the molecular axis and the transition moment of the chromophore was calculated as 59° or 121° for P r and 52° or 128° for P fr . These results explain well the polarotropic responses by phytochrome observed in plant organisms.