Expression, purification, crystallization and preliminary X‐ray crystallographic analysis of a novel plant‐type ferredoxin/thioredoxin reductase‐like protein from Methanosarcina acetivorans

The genome of Methanosarcina acetivorans contains a gene ( ma1659 ) that is predicted to encode an uncharacterized chimeric protein containing a plant‐type ferredoxin/thioredoxin reductase‐like catalytic domain in the N‐terminal region and a bacterial‐like rubredoxin domain in the C‐terminal region. To understand the structural and functional properties of the protein, the ma1659 gene was cloned and overexpressed in Escherichia coli . Crystals of the MA1659 protein were grown by the sitting‐drop method using 2  M ammonium sulfate, 0.1  M HEPES buffer pH 7.5 and 0.1  M urea. Diffraction data were collected to 2.8 Å resolution using the remote data‐collection feature of the Advanced Light Source, Lawrence Berkeley National Laboratory. The crystal belonged to the primitive cubic space group P 23 or P 2 1 3, with unit‐cell parameters a  =  b  =  c  = 92.72 Å. Assuming the presence of one molecule in the asymmetric unit gave a Matthews coefficient ( V M ) of 3.55 Å 3  Da −1 , corresponding to a solvent content of 65%.