Generally, a receptor and its associated hormone (or other chemical) ligand are often thought of as a lock-and-key, in which the ligand as the “key” fits perfectly into the receptor which is the “lock”. This results in a biological response––with “the key” ultimately being released intact from the receptor. Authors of the attached article, and another (independent) paper in Nat Chem Biol (by de Saint Germain et al.) show that the mechanism is different, … for a plant hormone family known as strigolactones.
The strigolactone receptor protein cleaves strigolactone and forms a covalent bond between the receptor and a cleaved hormone fragment called the D-ring. This triggers a dramatic change in the shape of the receptor, exposing surfaces that can interact with signaling partners. Analysis of Arabidopsis thaliana (tiny mustard plant) mutant d14-5 show that the AtD14(G158E) mutant maintains enzyme activity to hydrolyze strigolactone, but fails to efficiently interact with D3/MAX2 and loses the ability to act as a receptor that triggers strigolactone-signaling in plant cultures. These intriguing findings uncover a novel mechanism underlying the allosteric activation of AtD14 by strigolactone hydrolysis into a covalently-linked intermediate molecule, and define AtD14 as a noncanonical hormone receptor with dual functions to generate and sense the active form of strigolactone.
[ P.S. I see that the total size of attachments = ~21 MB, which might not be accepted by all email participants. 🙁 ]
Nature 25 Aug 2o16; 536: 469–473 [article] and pp 402–404 [News-N-Views]