Crystallization and preliminary X-ray diffraction analysis of the interaction ofAeromonas hydrophilaMtaN-1 withS-adenosylhomocysteine

Abstract

Prokaryotic 5′-methylthioadenosine/S-adenosylhomocysteine nucleosidase (MtaN) is a multifunctional enzyme that can hydrolyzeS-adenosyl-L-homocysteine (SAH) andS-methyl-5′-thioadenosine (MTA) to giveS-ribosyl-L-homocysteine (SRH) andS-methyl-5′-thioribose (MTR), respectively. This reaction plays a key role in several metabolic pathways, including biological methylation, polyamine biosynthesis, methionine recycling and bacterial quorum sensing. Structurally, MtaN belongs to the MtnN subfamily of the purine nucleoside phosphorylase (PNP)/uridine phosphorylase (UDP) phosphorylase family.Aeromonas hydrophilahas two MtnN subfamily proteins: MtaN-1, a periplasmic protein with an N-terminal signal sequence, and MtaN-2, a cytosolic protein. In this study, MtaN-1 fromAeromonas hydrophilawas successfully expressed and purified using Ni–NTA affinity, Q anion-exchange and gel-filtration chromatography. Crystals of the protein in complex with the substrate SAH were obtained and diffracted to a resolution of 1.4 Å. The crystals belonged to the trigonal space groupP3121 orP3221, with unit-cell parametersa=b= 102.7,c= 118.8 Å. The asymmetric unit contained two molecules of MtaN-1 complexed with SAH.