title: Stoichiometry of 2',5'-oligoadenylate-induced dimerization of ribonuclease L. A sedimentation equilibrium study.
abstract: Ribonuclease L is an endoribonuclease that is activated by binding of 2',5'-linked oligoadenylates. Activation of ribonuclease L also induces dimerization. Here, we demonstrate using equilibrium sedimentation that dimerization requires the binding of one 5'-monophosphate 2',5'-(adenosine)3 molecule per ribonuclease L monomer. No dimerization was observed in the absence of activator up to a protein concentration of 18 microM, indicating that unliganded enzyme is unable to dimerize or the association is very weak. In parallel with dimerization, enzymatic activity is also maximized at a 1:1 activator: ribonuclease L stoichiometry. The same stoichiometry for dimerization is observed using a nonphosphorylated activator 2'-5'-(adenosine)3. Adenosine triphosphate or RNA oligonucleotide substrates do not induce dimerization. The observed stoichiometry supports a model for ribonuclease L dimerization in which activator binds to monomer, which subsequently dimerizes.
authors.affiliation: Department of Biological Chemistry, Merck Research Laboratories, West Point, Pennsylvania 19486, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Cole
authors.forename: S S
authors.initials: SS
authors.lastname: Carroll
authors.forename: L C
authors.initials: LC
authors.lastname: Kuo
mesh_terms: D000227:Adenine Nucleotides / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000998:Antiviral Agents / Q000494:pharmacology*; D004722:Endoribonucleases / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D008962:Models, Theoretical; D009843:Oligoribonucleotides / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism
chemical_list: D000227:Adenine Nucleotides; D000998:Antiviral Agents; D046911:Macromolecular Substances; D009843:Oligoribonucleotides; D011994:Recombinant Proteins; C023505:2',5'-oligoadenylate; D000255:Adenosine Triphosphate; D004722:Endoribonucleases; C031956:2-5A-dependent ribonuclease