The Corynebacterium glutamicum aconitase repressor: scratching around for crystals

Crystallization of AcnR, a repressor of the aconitase gene in Corynebacterium glutamicum, is reported. Intentional manual scratching of the crystallization plates was applied to induce heterogeneous nucleation. Imperfections on the surfaces of crystallization containers are known to influence crystal formation and are thought to do so by helping to overcome the nucleation barrier. The intentional creation of imperfections has been widely applied to induce crystallization of small molecules, but has not been reported for protein crystallization. Here, the crystallization and preliminary X-ray analysis of the TetR-type aconitase repressor are reported. This regulator was the first transcription factor to be identified in the regulation of the tricarboxylic acid cycle in Corynebacterium glutamicum, an organism that is of special industrial interest and is an emerging model organism for Corynebacterineae. Successful crystallization involved introducing manual scratches on the surface of standard commercial plates, which led to a substantial improvement in crystal nucleation and quality