title: [Substrate specificity of T4 RNA-ligase: the role of a purine nucleotide base in forming a covalent AMP-RNA-ligase complex].
abstract: The NTP binding site of bacteriophage T4 RNA-ligase (EC 6.5.1.3) was studied using several ATP analogs modified in the purine moiety of the nucleotide at positions 1, 2, 6 and 8: adenosine-N'-oxide 5'-triphosphate (I), 6-chloropurine riboside 5'-triphosphate (II), 6-mercaptopurine riboside 5'-triphosphate (III), 1,N6-ethenoadenosine 5'-triphosphate (IV), 8-sulphoadenosine 5'-triphosphate (V), 8-bromoadenosine 5'-triphosphate (VI), inosine 5'-triphosphate (VII) and guanosine 5'-triphosphate (VIII). For all of the ATP analogs under study a reversible inhibition was demonstrated. These analogs appeared to be competitive inhibitors of the T4 RNA-ligase adenylation reaction and only V, VI and VII were efficient as substrates. The kinetic parameters for the competitive inhibition, (I50, Ki) were determined. A putative structure for the T4 RNA-ligase active site was proposed.
authors.forename: B A
authors.initials: BA
authors.lastname: Iuodka
authors.forename: D Ia
authors.initials: DIa
authors.lastname: Labeĭkite
authors.forename: S I
authors.initials: SI
authors.lastname: Sasnauskene
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives; D007700:Kinetics; D011685:Purine Nucleotides / Q000378:metabolism*; D011130:RNA Ligase (ATP) / Q000378:metabolism*; D013379:Substrate Specificity; D013604:T-Phages / Q000201:enzymology*
chemical_list: D011685:Purine Nucleotides; D000255:Adenosine Triphosphate; D011130:RNA Ligase (ATP)
vernacular_title: Substratnaia spetsifichenost' T4-RNK-ligazy: rol' purinovogo osnovaniia nukleotida v obrazovanii kovalentnogo AMP-RNK-ligaznogo kompleksa.