RESUMO
Crotin II isolated from the seeds of Euphorbiacea Croton tiglium has been crystallized. Crystals were grown by vapor diffusion using KCl as the precipitant. The crystal of crotin II belongs to the space group P6(1) or P6(5) with cell parameters a = b = 94.62 A, c = 28.43 A, alpha = beta = 90 degrees, gamma = 120 degrees. The asymmetric unit contains one molecule of 15,000 Da. A data set to 1.82 A has been collected on an area detector.
Assuntos
Proteínas de Plantas/química , Inibidores da Síntese de Proteínas/química , Cristalização , Cristalografia por Raios X , Proteínas de Plantas/isolamento & purificação , Conformação Proteica , Inibidores da Síntese de Proteínas/isolamento & purificação , Proteínas Inativadoras de Ribossomos Tipo 1 , Ribossomos/efeitos dos fármacos , SementesRESUMO
The crystallographic refinement of trichosanthin has been performed at 2.6 A resolution. The crystal and molecular structure of trichosanthin is described in detail in this paper. On summarizing the regularity of the amino acid sequences of eight kinds of ribosome inactivating proteins and combining with the crystal and molecular structure of trichosanthin, fifteen most conservative amino acid residues are analyzed. It is found that four most conservative polar amino acid residues Gln156, Glu160, Arg163 and Glu189 gather on the molecular surface on the boundary of the large and small domains, thus forming the active center of the protein molecule.
Assuntos
Estrutura Secundária de Proteína , Tricosantina/química , Sequência de Aminoácidos , Cristalografia , Conformação Molecular , Dados de Sequência Molecular , Estrutura MolecularRESUMO
The molecule model of trichosanthin has been rebuilt by using the electron density map improved by the solvent flatten and in accordance with the primary structure put forward by Collins. The crystallographic refinement of two trichosanthin molecules (3828 nonhydrogen atoms) in an asymmetric unit has been carried out by means of the restrain least-square procedure and diffraction data to a resolution of 2.6 A. The results are: an R factor 0.223 and the r.m.s. deviation of the bond length = 0.023 A. The new molecular model is in good agreement with the electron density map calculated with the coefficient 2Fo-Fc.
Assuntos
Tricosantina/química , Cristalografia , Conformação Molecular , Estrutura MolecularRESUMO
A model completed recently of two trichosanthin molecules in an asymmetric unit belonging to the monoclinic system is reported. It can be seen that the molecular structure consists of two domains, one large and one small, and that there are some features in the secondary structure. The dissimilarity between two molecules as well as their interactions in an independent unit correlated in a non-symmetric way has been described, moreover, the binding sites of the heavyatom position in the derivatives are also discussed.