ISOLATION, CRYSTALLIZATION AND X-RAY-ANALYSIS OF THE QUATERNARY COMPLEX OF PHE-TRNA(PHE), EF-TU, A GTP ANALOG AND KIRROMYCIN

Kirromycin inhibits bacterial protein synthesis by acting on elongatio n factor Tu (EF-Tu). Complexes of the antibiotic, Phe-tRNA(Phe), the g uanosine triphosphate analog GDPNP, and mesophilic (Escherichia coli), as well as thermophilic (Thermus thermophilus) EF-Tu were isolated. C rystallization was achieved at 4 degrees C, pH 6.4, using ammonium sul phate as precipitant. Crystallographic data were recorded at cryogenic temperature on crystals exposed to synchrotron radiation. Crystals of the thermophilic complex are based on a rhombohedral lattice with cel l dimensions of 137.3 Angstrom, and angles of 54.0 degrees. Although r elated, these cell parameters are different from those found in the cr ystals of the recently solved structure of the ternary complex of Phe- tRNA(Phe), GDPNP, and Thermus aquaticus EF-Tu (Nissen, P., Kjeldgaard, M., Thirup, S., Polekhina, G., Reshetnikova, L., Clark, B.F. and Nybo rg, J. (1995) Science 270, 1464-1472 [1]), possibly indicating some al losteric effect caused by kirromycin. Crystals of the mesophilic compl ex belong to the cubic space P432, with cell axis of 196.26 Angstrom. In both cases, the crystals contain one complex per asymmetric unit.