Arabidopsis thaliana DGAT3 is a [2Fe-2S] protein involved in TAG biosynthesis

Laure Aymé,Ornella Bimai,Nadia Touati,Franjo Jagic,Sébastien Baud,Simon Arragain,Michel Canonge,Pierre Briozzo,Marc Fontecave,Christelle Louis-Mondésir,Thierry Chardot

doi:10.1038/s41598-018-35545-7

Abstract

Acyl-CoA:diacylglycerol acyltransferases 3 (DGAT3) are described as plant cytosolic enzymes synthesizing triacylglycerol. Their protein sequences exhibit a thioredoxin-like ferredoxin domain typical of a class of ferredoxins harboring a [2Fe-2S] cluster. The Arabidopsis thaliana DGAT3 (AtDGAT3; At1g48300) protein is detected in germinating seeds. The recombinant purified protein produced from Escherichia coli, although very unstable, exhibits DGAT activity in vitro. A shorter protein version devoid of its N-terminal putative chloroplast transit peptide, Δ46AtDGAT3, was more stable in vitro, allowing biochemical and spectroscopic characterization. The results obtained demonstrate the presence of a [2Fe-2S] cluster in the protein. To date, AtDGAT3 is the first metalloprotein described as a DGAT.

Highlights

Eukaryotic DGATs are classified in three distinct classes
We demonstrated that Arabidopsis thaliana DGAT3 (AtDGAT3) was active
AtDGAT3 contains a thioredoxin-like ferredoxin domain conserved among members of the DGAT3 family

Summary

Introduction

Eukaryotic DGATs are classified in three distinct classes. DGAT1 and 2 types are integral membrane proteins of the endoplasmic reticulum[7,8,9,10] whereas DGAT3 are soluble proteins[11,12,13]. Two other isoforms were identified in peanut: AhDGAT3-2 and AhDGAT3-3 The latter was functionally characterized by heterologous expression in yeast[11]. Other soluble plant acyltransferases have been identified over the past decades[27,28,29,30] The DGAT activity of AtDGAT3 still needs to be validated in vitro with the purified protein, or in vivo by functional complementation of a mutant defective in TAG synthesis. The presence of a thioredoxin-like ferredoxin domain, intriguing for a predicted DGAT, does not convey precise information on the activity of the protein[31] and raises questions about its possible biochemical function

Methods

Results

Conclusion