Salts induce structural changes in @entity70732 from the hyperthermophilic archaeon XXXX : a Fourier transform infrared spectroscopic study.

@entity3007 @entity8777 @entity70733 @entity12204 @entity1219 @entity1372 @entity70732 @entity3006 @entity15403 @entity6346 @entity4338
@entity70732 from the hyperthermophilic archaeon @entity12204 ( @entity70733 ) carries the aminoacyl tRNA to the ribosome; it binds @entity3006 or @entity3007 , and it is also endowed with an intrinsic GTPase activity that is triggered in vitro by @entity1219 at molar concentrations [Masullo, M., De Vendittis, E., and Bocchini, V. (1994) J. Biol. Chem. 269, 20376-20379]. The structural properties of @entity70733 were investigated by Fourier transform infrared spectroscopy. The estimation of the secondary structure of the @entity70733 * @entity3006 complex, made by curve fitting of the @entity6346 I' band or by factor analysis of the @entity6346 I band, indicated a content of 34-36% alpha-helix, 35-40% beta-sheet, 14-19% turn, and 7% unordered structure. The substitution of the @entity3006 bound with the slowly hydrolyzable GTP analogue Gpp(NH)p induced a slight increase in the alpha-helix and beta-sheet content. On the other hand, the alpha-helix content of the @entity70733 * @entity3006 complex increased upon addition of salts, and the highest effect was produced by 5 M @entity1219 . The thermal stability of the @entity70733 * @entity3006 complex was significantly reduced when the @entity3006 was replaced with Gpp(NH)p or in the presence of @entity15403 or @entity8777 , whereas a lower destabilizing effect was provoked by @entity1219 and @entity4338 . Therefore, the extent of the destabilizing effect of salts depended on the nature of both the cation and the anion. The data suggested that the @entity1372 ion was responsible for the induction of the GTPase activity, whereas the anion modulated the enzymatic activity through destabilization of particular regions of @entity70733 . Finally, the infrared data suggested that, in particular region(s) of the polypeptide chain, the @entity70733 *Gpp(NH)p complex possesses structural conformations which are different from those present in the @entity70733 * @entity3006 complex.
