The ACT domain in chloroplast precursor–phosphorylating STY kinases binds metabolites and allosterically regulates kinase activity


Ahmed Eisaa, Bettina Böltera and Serena Schwenkert

Journal of Biological Chemistry
2019 Oct 8. doi: 10.1074/jbc.RA119.010298


Protein import of nuclear- encoded proteins into plant chloroplasts is a highly regulated process, requiring fine-tuning mechanisms especially during chloroplast differentiation. One way of altering the import efficiency is achieved by phosphorylation of chloroplast transit peptides in the cytosol. Recently, we have investigated the role of three serine/threonine/tyrosine (STY) kinases, STY8, STY17, and STY46, in precursor phosphorylation. These three kinases share a high degree of similarity and harbor a conserved ACT domain upstream of the kinase domain. The ACT domain is a widely distributed structural motif, known to be important for the allosteric regulation of many enzymes. In this work, using biochemical and biophysical techniques both in vitro and in planta, including kinase assays, microscale thermophoresis, size-exclusion chromatography, as well as site-directed mutagenesis approaches, we show that the ACT domain regulates autophosphorylation and substrate phosphorylation of the STY kinases. We found that isoleucine and S-adenosylmethionine bind to the ACT domain, negatively influencing its autophosphorylation ability. Moreover, we investigated the role of the ACT domain in planta and confirmed its involvement in chloroplast differentiation in vivo. Our results provide detailed insights into the regulation of enzyme activity by ACT domains and establish that it has a role in binding amino acid ligands during chloroplast biogenesis.

View Publication

Topics: Plant proteins, Monolith – MicroScale Thermophoresis, MST, Proteins, Publications



No Previous Articles

Up next
Trehalose 6-phosphate positively regulates fatty acid synthesis by stabilizing WRINKLED1
Trehalose 6-phosphate positively regulates fatty acid synthesis by stabilizing WRINKLED1


Sign up to receive
the latest NanoTemper news, product updates, event announcements and more

First Name
Last Name
Company Name
Agree to Subscribe & Privacy Policy*
*I have fully read, understood and agree to the Privacy Policy. I accept the storing and processing of my personal data by NanoTemper as described in the Privacy Policy.

By completing this form, you provide us consent to contact you with educational content, news and information about our products, services and events. You may unsubscribe at any time.
Thank you!
Error - something went wrong!