Dodecamers derived from the crystal structure were found in the pre-crystallization solution of the transaminase from the thermophilic bacterium Thermobaculum terrenum by small-angle X-ray scattering

The pre-crystallization solution of the transaminase from Thermobaculum terrenum (TaTT) has been studied by small-angle X-ray scattering (SAXS). Regular changes in the oligomeric composition of the protein were observed after the addition of the precipitant. Comparison of the observed oligomers with the crystal structure of TaTT (PDB ID 6GKR) shows that dodecamers may act as building blocks in the growth of transaminase single crystals. Correlating of these results to the similar X-ray studies of other proteins suggests that SAXS may be a valuable tool for searching optimum crystallization conditions. AbbreviationSAXSsmall-angle X-ray scatteringTatransaminaseTaTTtransaminase from Thermobaculum terrenumPLPpyridoxal-5'-phosphateR-PEAR-(þ)-1-phenylethylamineBCATbranched-chain amino acid aminotransferaseDAATD-aminoacid aminotransferaseR-TAR-amine:pyruvate transaminaseCommunicated by Ramaswamy H. Sarma.

Octamer formation in lysozyme solutions at the initial crystallization stage detected by small-angle neutron scattering

Solutions of lysozyme in heavy water were studied by small-angle neutron scattering (SANS) at concentrations of 40, 20 and 10 mg ml^-1 with and without the addition of precipitant, and at temperatures of 10, 20 and 30°C. In addition to the expected protein monomers, dimeric and octameric species were identified in solutions at the maximum concentration and close to the optimal conditions for crystallization. An optimal temperature for octamer formation was identified and both deviation from this temperature and a reduction in protein concentration led to a significant decrease in the volume fractions of octamers detected. In the absence of precipitant, only monomers and a minor fraction of dimers are present in solution.