N-terminal domain of Avena phytochrome: interactions with sodium dodecyl sulfate micelles and N-terminal chain truncated phytochrome.
Phytochrome is the ubiquitous red light photoreceptor present in plants. Properties of the 6-kDa end terminal region of phytochrome A (PHYA from etiolated Avena) have been investigated by the use of synthetic polypeptide fragments corresponding to that region. This region of the phytochrome A protein has been viewed as a possible functional site due to the large differences in the sequence's conformation and exposure between the Pr (red light-absorbing form) and Pfr (far-red light-absorbing, gene-regulating form) species of phytochrome A. Hydrophobic moment calculations reveal amphiphilic helical potential in this section of the protein, consistent with the folding of the N-terminal region onto a hydrophobic chromophore/chromophore pocket. A large N-terminal synthetic peptide also demonstrated helical folding in the presence of SDS micelles. This experimental evidence indicates that the N-terminal alpha-helical folding upon conversion of the regulatorily inactive Pr to the active Pfr form of phytochrome A is likely driven at least in part by amphiphilic helix stabilization. Further, the large synthetic peptide was spectrally demonstrated to interact with phytochrome A lacking the N-terminal region. The formation of this nativelike complex may provide us with a tool for both biophysical and physiological studies on the mechanism of phytochrome A signal transduction.
Parker
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Department of Chemistry, University of Nebraska, Lincoln 68588.
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D002523:Edible Grain; D008823:Micelles; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D010775:Photic Stimulation; D010834:Phytochrome / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D017433:Protein Structure, Secondary; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D013057:Spectrum Analysis
D008823:Micelles; D010446:Peptide Fragments; D010834:Phytochrome; D012967:Sodium Dodecyl Sulfate