Crystallization and preliminary crystallographic analysis of nosiheptide‐resistance methyltransferase from Streptomyces actuosus in complex with SAM

Nosiheptide‐resistance methyltransferase (NSR) methylates 23S rRNA at the nucleotide adenosine 1067 in Escherichia coli and thus contributes to resistance against nosiheptide, a sulfur‐containing peptide antibiotic. Here, the expression, purification and crystallization of NSR from Streptomyces actuosus are reported. Diffracting crystals were grown by the hanging‐drop vapour‐diffusion method in reservoir solution consisting of 0.35  M ammonium chloride, 24%( w / v ) PEG 3350, 0.1  M MES pH 5.7 at 293 K. Native data have been collected from the apo enzyme and a SAM complex, as well as apo SeMet SAD data. The diffraction patterns of the apo form of NSR, of NSR complexed with SAM and of SeMet‐labelled NSR crystals extended to 1.90, 1.95 and 2.25 Å resolution, respectively, using synchrotron radiation. All crystals belonged to space group P 2 1 , with approximate unit‐cell parameters a = 64.6, b = 69.6, c  = 64.9 Å, β = 117.8°.