Nucleic Acids Research, 1977, Vol. 4, No. 10 3627-3642
© 1977
Articles |
Complex formation between ribosomal protein S1, oligo-and polynucleotides: chain length dependence and base specificity
Fachgebiet Biochemie der Technischen Hochschule Darmstadt Petersenstr. 22, D-6100 Darmstadt, GFR
Received August 8, 1977. In order to examine the nature of the complex formation between the ribosomal protein S1 and nucleic acids three methods were used: Inhibition of the reaction of N-ethy|2.314C|-maleimide with S1 by the addition of oligonucleotides; adsorption of the complexes to nitrocellulose filters; and equilibrium dialysis. The complex formation is Mg2+ dependent at low salt concentrations and becomes Mg2+ independent at an ionic strength greater than 90 mM. Oligouridylates of increasing chain length reach an optimal KA of 3.3.107 M-1 at a chain length of n = 13–14. Protein S1 contains one binding site for long chain oligouridylates, such as U12, and the standard-free-energy change of binding caused by one pU increment is 0.41 kcal/mol, when n varies between five and fourteen. Complex formation is insensitive to the capacity of the homopolynucleo-tide bases to form hydrogen bonds. Homopolynucleotides, however, showing a Tm < 25° in the buffer system used show an increased affinity for S1 compared to poly(A) and poly(C) (Tm > 40°). The data are discussed with respect to the proposed binding of protein S1 to the 3'terminal end of the 16S RNA.