1mrk
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STUDIES ON CRYSTAL STRUCTURES ACTIVE CENTER GEOMETRY AND DEPURINE MECHANISM OF TWO RIBOSOME-INACTIVATING PROTEINS
OverviewOverview
Two ribosome-inactivating proteins, trichosanthin and alpha-momorcharin, have been studied in the forms of complexes with ATP or formycin, by an, X-ray-crystallographic method at 1.6-2.0 A (0.16-0.20 nm) resolution. The, native alpha-momorcharin had been studied at 2.2 A resolution. Structures, of trichosanthin were determined by a multiple isomorphous replacement, method. Structures of alpha-momorcharin were determined by a molecular, replacement method using refined trichosanthin as the searching model., Small ligands in all these complexes have been recognized and built on the, difference in electron density. All these structures have been refined to, achieve good results, both in terms of crystallography and of ideal, geometry. These two proteins show considerable similarity in their, three-dimensional folding and to that of related proteins. On the basis of, these structures, detailed geometries of the active centres of these two, proteins are described and are compared with those of related proteins. In, all complexes the interactions between ligand atoms and protein atoms, including hydrophobic forces, aromatic stacking interactions and hydrogen, bonds, are found to be specific towards the adenine base. The relationship, between the sequence conservation of ribosome-inactivating proteins and, their active-centre geometry was analysed. A depurinating mechanism of, ribosome-inactivating proteins is proposed on the basis of these results., The N-7 atom of the substrate base group is proposed to be protonated by, an acidic residue in the active centre.
About this StructureAbout this Structure
1MRK is a Single protein structure of sequence from Trichosanthes kirilowii with FMC as ligand. Full crystallographic information is available from OCA.
ReferenceReference
Studies on crystal structures, active-centre geometry and depurinating mechanism of two ribosome-inactivating proteins., Huang Q, Liu S, Tang Y, Jin S, Wang Y, Biochem J. 1995 Jul 1;309 ( Pt 1):285-98. PMID:7619070
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