Photoreversible circular dichroism spectral change in oat phytochrome is suppressed by a monoclonal antibody that binds near its N-terminus and by chromophore modification

Journal Article · Tue Aug 11 00:00:00 EDT 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00390a010· OSTI ID:5902595

Chai, Y G; Song, P S; Cordonnier, M M; Pratt, L H

Accompanying the phototransformation of native 124-kilodalton (kDa) oat phytochrome from red-absorbing form (Pr) to far-red-absorbing form (Pfr), there is a photoreversible change in circular dichroism (CD) in the far-UV region indicative of a 3% increase in ..cap alpha..-helical folding of apoprotein. To elucidate the conformational change involved in the phytochrome phototransformation, several monoclonal antibodies have been used as epitope-specific probes. Monoclonal antibody oat-25 suppressed the photoreversible CD spectral change using phytochrome with an A/sub 666//A/sub 280/ as Pr of 1.13. Monoclonal antibodies oat-22, oat-13, and oat-31 did not significantly affect the CD spectral change of phytochrome. Oat-25 requires an epitope near the N-terminus of phytochrome. Oat-22, oat-13, and oat-31 recognize epitopes on the N-terminus, chromophore-containing half of phytochrome, albeit further removed from the N-terminus than that recognized by oat-25. Interestingly, oat-13 and oat-31 did, however, induce a time-dependent decrease in the far-UV CD, apparently due to aggregation of phytochrome (both Pr and Pfr forms). Monoclonal antibodies oat-26 and oat-28, which recognize epitopes on the C-terminus half of phytochrome, also did not suppress the photoreversible CD change, although oat-26 and oat-28 slightly inhibited it. The photoreversible CD spectral change can also be inhibited by sodium borohydride, which bleaches the chromophore by reducing it, and by tetranitromethane, which oxidizes the chromophore of phytochrome. Although explanations of these results based on indirect interactions between the chromophore and the N-terminus segment are possible, the authors propose that an additional ..cap alpha..-helical folding of the Pfr form of the phytochrome may result from a photoreversible interaction between the Pfr form of the chromophore and the N-terminus segment.

• Research Organization: Texas Tech Univ., Lubbock
• OSTI ID: 5902595
• Journal Information: Biochemistry; (United States), Vol. 26:16
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
MONOCLONAL ANTIBODIES
ULTRAVIOLET SPECTRA
PHYTOCHROMES
CONFORMATIONAL CHANGES
MAGNETIC CIRCULAR DICHROISM
FAR ULTRAVIOLET RADIATION
OATS
PHOTOCHEMISTRY
ANTIBODIES
CEREALS
CHEMISTRY
DICHROISM
ELECTROMAGNETIC RADIATION
GRASS
ORGANIC COMPOUNDS
PIGMENTS
PLANTS
PROTEINS
RADIATIONS
SPECTRA
ULTRAVIOLET RADIATION
140505* - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)