Expression, purification, crystallization and preliminary X-ray diffraction studies of the cmcI component of Streptomyces clavuligerus 7α-­cephem-methoxylase

Cephamycins are broad-spectrum β-lactam antibiotics that show resistance to certain forms of β-lactamases. They differ from cephalosporins by the presence of a methoxyl group at the C-7α position. The gene products of cmcI and cmcJ are believed to control 7α-methoxylation of cephalosporins through successive steps of hydroxylation and methylation. Here, the expression, purification, crystallization and initial data-collection statistics of the 236-­amino-acid protein product of cmcI from Streptomyces clavuligerus is reported. The crystals belong to space group P2₁, with unit-cell parameters a = 93.6, b = 182.6, c = 103.2 Å, β = 91.05°. Diffraction data were collected to 2.5 Å.