| Summary: | Protein crystallization can serve as a purification step in biotechnological processes but is often limited by the non-crystallizability of proteins. Enabling or improving crystallization is mostly achieved by high-throughput screening of crystallization conditions and, more recently, by rational crystal contact engineering. Two selected rational crystal contact mutations, Q126K and T102E, were transferred from the alcohol dehydrogenases of <i>Lactobacillus brevis</i> (<i>Lb</i>ADH) to <i>Lactobacillus kefir</i> (<i>Lk</i>ADH). Proteins were expressed in <i>E. coli</i> and batch protein crystallization was performed in stirred crystallizers. Highly similar crystal packing of <i>Lk</i>ADH wild type compared to <i>Lb</i>ADH, which is necessary for the transfer of crystal contact engineering strategies, was achieved by aligning purification tag and crystallization conditions, as shown by X-ray diffraction. After comparing the crystal sizes after crystallization of <i>Lk</i>ADH mutants with the wild type, the mean protein crystal size of <i>Lk</i>ADH mutants was reduced by 40–70% in length with a concomitant increase in the total amount of crystals (higher number of nucleation events). Applying this measure to the <i>Lk</i>ADH variants studied results in an order of crystallizability T102E > Q126K > <i>Lk</i>ADH wild type, which corresponds to the results with <i>Lb</i>ADH mutants and shows, for the first time, the successful transfer of crystal contact engineering strategies.
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