Crystallization and preliminary X-ray studies of the Ia component of Clostridium perfringens iota toxin complexed with NADPH

A recombinant Ia component of Clostridium perfringens iota toxin, which ADP -ribosylates actin, was crystallized by the hanging drop vapor diffusion me thod using PEG4000 as a precipitating agent. The crystals were obtained in the presence of NADPH, which is similar to a real substrate, NADH, and belo ngs to the space group P1 (a = 47.9 Angstrom b = 54.5 Angstrom, c = 103.1 A ngstrom, alpha = 99.0 degrees, beta = 93.3 degrees, and gamma = 107.2 degre es). The Matthews coefficient of native crystal was 2.7, assuming 2 mol/asy mmetric unit. Native data were collected at 2.4-Angstrom resolution. The re sults from a heavy-atom search showed that lanthanide ions (samarium, holmi um) altered the molecular packing, judging from the unit-cell difference. T he crystals also belonged to the space group P1 (a = 47.7 Angstrom, b = 53. 9 Angstrom, c = 54.6 Angstrom, alpha = 68.9 degrees, beta = 78.3 degrees, a nd gamma = 73.7 degrees), which is consistent with only one molecule per as ymmetric unit. (C) 1999 Academic Press.