Recapitulating the Structural Evolution of Redox Regulation in Adenosine 5′-Phosphosulfate Kinase from Cyanobacteria to Plants

Jonathan Herrmann,David Nathin,Soon Goo Lee,Tony Sun,Joseph M Jez

doi:10.1074/jbc.m115.679514

Jonathan Herrmann, David Nathin + Show 3 more

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https://doi.org/10.1074/jbc.m115.679514

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Abstract

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 revealed the overall structure of the enzyme, which lacks the NTD found in homologs from mosses and plants. A series of engineered SynAPSK variants reconstructed 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 showed that the addition of the NTD and cysteines recapitulated thiol-based regulation. These results reveal the molecular basis for structural changes leading to the evolution of redox control of APSK in the green lineage from cyanobacteria to plants.

Highlights

In the plant sulfur assimilation pathway, adenosine 5؅-phosphosulfate (APS) kinase is a redox-regulated branch point enzyme
The use of APS (Fig. 1A), a high energy molecule with twice the energy of the pyrophosphate linkage of ATP [43,44,45], for incorporation of sulfur into compounds of primary and specialized metabolism places constraints on the protein structure required for recognizing this special metabolite
The enzymes responsible for producing APS (ATP sulfurylase) and its conversion to useable forms (APS kinase) are highly conserved in sequence and core structure across a wide range of organisms [18, 46]; these enzymes display a remarkable variety in domain organization/ architecture and regulatory features

Summary

Introduction

In the plant sulfur assimilation pathway, APS kinase is a redox-regulated branch point enzyme. 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. Biochemical analyses of SynAPSK, SynAPSK H23C mutant, SynAPSK fused to the AtAPSK NTD, and the fusion protein with the H23C mutation showed that the addition of the NTD and cysteines recapitulated thiol-based regulation. These results reveal the molecular basis for structural changes leading to the evolution of redox control of APSK in the green lineage from cyanobacteria to plants

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