Differences in the thermostability of the red- and far- red-absorbing forms of oat phytochrome

Abstract

A comparative analysis of the ability to reversibly phototransform after heating of the red-absorbing form of phytochrome (P R) and far-red-absorbing (P FR) form of native oat phytochrome has been carried out. Although the P FR spectrum is more affected at elevated temperatures (40–50 °C), this form is denatured more slowly than P R. Direct evidence for the chromoprotein conformation stabilization upon phototransformation of P R to P FR has been obtained. Photocycling phytochrome forms at elevated temperatures makes an additional contribution to the chromoprotein denaturation.