Combining crystallogenesis methods to produce diffraction-quality crystals of a psychrophilic tRNA-maturation enzyme.

The determination of conditions for the reproducible growth of well diffracting crystals is a critical step in every biocrystallographic study. On the occasion of a new structural biology project, several advanced crystallogenesis approaches were tested in order to increase the success rate of crystallization. These methods included screening by microseed matrix screening, optimization by counter-diffusion and crystal detection by trace fluorescent labeling, and are easily accessible to any laboratory. Their combination proved to be particularly efficient in the case of the target, a 48 kDa CCA-adding enzyme from the psychrophilic bacterium Planococcus halocryophilus. A workflow summarizes the overall strategy, which led to the production of crystals that diffracted to better than 2 Å resolution and may be of general interest for a variety of applications.