Scientists unlock why plants sense red light the same way every time
Researchers have solved a decades-old puzzle about how plants detect light by identifying the precise molecular mechanism that governs photoreceptor activation. The finding could accelerate development of crops engineered to respond better to changing light conditions, a key advantage as climate variability increases.
Originaltitel: Steric Effects Govern the Photoactivation of Phytochromes
<p>Phytochromes constitute a superfamily of photoreceptor proteins existing in two forms that absorb red (Pr) and far-red (Pfr) light. Although it is well-known that the conversion of Pr into Pfr (the biologically active form) is triggered by a ZE photoisomerization of the linear tetrapyrrole chromophore, direct evidence is scarce as to why this reaction always occurs at the methine bridge between pyrrole rings C and D. Here, we present hybrid quantum mechanics/molecular mechanics calculations based on a high-resolution Pr crystal structure of Deinococcus radiodurans bacteriophytochrome to investigate the competition between all possible photoisomerizations at the three different (AB, BC and CD) methine bridges. The results demonstrate that steric interactions with the protein are a key discriminator between the different reaction channels. In particular, it is found that such interactions render photoisomerizations at the AB and BC bridges much less probable than photoisomerization at the CD bridge.</p>