Biopolymers and cell. 1986. Volume 2. № 2. 106 - 111

M. P. Kirpichnikov, A. P. Yartsev, L. E. Minchcnkova, B. K. Chernov, V. I. Ivanov

SPECIFIC INTERACTION OF THE cro-REPRESSOR WITH OPERATOR SITE MODELS. CIRCULAR DICHROISM STUDIES

Summary

    The circular dichroism (CD) method was used to study the interaction of the crorepressor of the phage A. with a synthetic On3 operator of 17 base pairs long, and with its 9 base pairs fragment

                                    5'  TATCCCTT  [GCGGTGATA]

                                    3' ATAGGGAA [CGCCACTAT]

 In both cases addition of cro-protein considerably changed the CD spectra in the region of 260-300 nm. The stoichiometry determined by the CD titration is identical both for OR3 and its fragment: one duplex per cro dimer. The interaction of the cro-protein with non-operator DNAs reveals no visible CD changes at all. The spectral changes during specific interaction are quite different from those for the B-A transition and for winding of the DNA within the B-family towards C-form. A conclusion is drawn that the CD changes are mainly induced by the CD effect in Tyr-26 during specific complex formation, the operator DNA conformation being conserved in a B-like form as a whole.
Summary in Russian