title: [Physico-chemical properties of ribonuclease A modified with pyridoxal-5'-phosphate].
abstract: The physico-chemical properties have been studied of RNase A selectively modified at the E-NH2-group of Lys-7 and Lys-41 with pyridoxal-P. Modification did not affect conformational stability of the protein globule, thus all changes in the molecule of the modified RNase A were localised around the alkylated Lys residue. In the both cases pyridoxyl-P. The residue was shown to be localized in the active site region of the (P-Pxy)-Lys-7-RNase A and its chromophore parts was highly exposed to the solvent. (P-Pxy) E-Lys-7-RNase A and its chromophore parts was highly exposed to the solvent. In the Lys-41 derivative, pyridoxamine-P was situated exactly in the active site and is partially hidden in the protein grobule. The pH-dependence of absorption spectra indicates that the chromophore of pyridoxyl-P in modified proteins is quite sensible to the ionic state of its surrounding. The usefulness of pyridoxyl-P as a reporter group was proved in the study with (P-Pxy)-Lys-7-RNase A. Some conformational changes involving His-119 were shown to take place in the course of the enzyme-nucleotide complex formation.
mesh_terms: D001665:Binding Sites; D002942:Circular Dichroism; D004355:Drug Stability; D011487:Protein Conformation; D012260:Ribonucleases; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature
chemical_list: D012260:Ribonucleases
vernacular_title: Fiziko-khimicheskie svoĭstva ribonukleazy A, modifitsirovannoĭ piridoksal'-5'-fosfatom