Recapitulating the Structural Evolution of Redox-Regulation in Adenosine-5′-Phosphosulfate Kinase from Cyanobacteria to Plants [Protein Structure and Folding]

August 20th, 2015 by Herrmann, J., Nathin, D., Lee, S. G., Sun, T., Jez, J. M.

In plants, adenosine 5'-phosphosulfate (APS) kinase (APSK) is required for reproductive viability and the production of 3'-phosphoadenosine-5'-phosphosulfate (PAPS) as a sulfur-donor in specialized metabolism. Previous studies of the APSK from Arabidopsis thaliana (AtAPSK) identified a regulatory disulfide bond formed between the N-terminal domain (NTD) and a cysteine on the core scaffold. This thiol-switch is unique to mosses, gymnosperms, and angiosperms. To understand the structural evolution of redox-control of APSK, we investigated the redox-insensitive APSK from the cyanobacterium Synechocystis sp. PCC 6803 (SynAPSK). Crystallographic analysis of SynAPSK in complex with either APS and a non-hydrolyzable ATP analog or APS and sulfate reveals the overall structure of the enzyme, which lacks the NTD found in homologs from mosses and plants. A series of engineered SynAPSK variants reconstruct the structural evolution of the plant APSK. Biochemical analyses of SynAPSK, SynAPSK H23C mutant, SynAPSK fused to the AtAPSK NTD, and the fusion protein with the H23C mutation show that addition of the NTD and cysteines recapitulates thiol-based regulation. These results reveal the molecular basis for structural changes leading to the evolution of redox-control in APSK of the green lineage from cyanobacteria to plants.
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