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Photochromism and dimerization of pea phytochrome A
Abstract
Phytochromes are photochromic proteins that induce photomorphogenic and developmental responses in plants. The molecular basis of the photo-signal transduction is the result of the photoinduced change between the Pr and Pfr forms of the phytochromes. The remarkable photochromism of pea phytochrome A can be partly described in terms of only a small number of specific amino acid residues. Histidine-324 appears to serve as an anchimeric catalytic residue for the chromophore ligation and as hydrogen bonding function for the photochromism. Isoleucine-80 plays an important role as a hydrophobic residue for the chromophore ligation and photochromism. Arginine-383 is presumably within the chromophore pocket and plays a critical role for the stabilization of Pfr form for phytochrome photochromism. Apparently, the chromophore pocket entails the amphiphilic α-helix backbone centered around residue 391, reminiscent of the amphiphilic helices in other tetrapyrrole/heme-containing proteins. Phytochrome A exists as a homologous dimer. There are two major domains in phytochrome A, the N-terminal domain (65 kDa) responsible for the chromophore attachment and its photochromism, and the C-terminal domain (60 kDa) responsible for the dimerization which is important for its regulatory function. The dimerization motifs were studied by means of a novel yeast two-hybrid in vivo protein-protein interaction assay system. After analysis of several internal deletions, truncations and site-specific mutants of pea phytochrome A C-terminal domain, we found that the primary contact region for the dimerization is V 730-F821. The residues from 780 through 800 are most important for the dimerization.
Subject Area
Botany
Recommended Citation
Bhoo, Seong Hee, "Photochromism and dimerization of pea phytochrome A" (1998). ETD collection for University of Nebraska-Lincoln. AAI9917822.
https://digitalcommons.unl.edu/dissertations/AAI9917822