Nucleic Acids Research, 1981, Vol. 9, No. 10 2367-2385
© 1981
MOLECULAR BIOLOGY |
Mechanism of the interaction between ribosomal protein S1 and oligonucleotides
*Institut für Physikalische Biologie, Universität Düsseldorf, Universitätsstrasse 1 4000 Düsseldorf +Institut für Organische Chemie und Biochemie, Technische Hochschule Darmstadt Petersenstrasse 22, 6100 Darmstadt, GFR
Received March 16, 1981. The interaction of the ribosomal protein S1 from E. coli MRE 600 with oligonucleotides was studied by hydrodynamic, spectrophotometric, and kinetic methods.
UV-difference spectra which are induced by the complex formation could be separated into a hyperchromic contribution originating from the nucleic acid moiety and a hypochromic contribution from the protein. Systematic determination of binding and rate constants was carried out by the temperature-jump relaxation technique. From the quantitative evaluation of the relaxation times and the relaxation amplitudes, the following conclusions could be drawn: The stoichiometry of the complex formation is one mole S1 per one mole oligonucleotide. The binding constant K, the recombination rate constant kR, and the dissociation rate constant kD, respectively, were measured at different temperatures. The values at 10°C are K = 2.106 M1, kR = 1.3.108 M1s1, kD = 65 s1 for A(pA)12 and K = 7.5.105 M1, kR =6.8.107 M1s1kD = 90 s1 for U(pU)12. Discrepancies with data reported elsewhere are discussed.
The stacking-unstacking equilibrium of the free oligonucleotide is frozen if the oligonucleotide is bound to the protein. The conformational change of the oligonucleotide does not occur in the form of a preequilibrium, but is induced after the primary binding step.