Transition-Metal Complexes as Inhibitors of Proteins Recognizing Double-Stranded Fragments of Nucleic Acids

N. F. Krynetskaya¹, E. A. Kubareva^2*, M. A. Timchenko¹, V. M. Belkov¹, and Z. A. Shabarova¹

¹School of Chemistry and ²Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119899 Russia; fax: (095) 939-3181; E-mail: kubareva@genebee.msu.su

^* To whom correspondence should be addressed.

Received December 11, 1997; Revision received April 27, 1998

---

A 30-membered DNA duplex containing the recognition site of restriction endonuclease SsoII and a 30-membered RNA--DNA hybrid duplex, a substrate of E. coli RNase H, were synthesized. The cleavage of the 30-membered fragments of nucleic acids catalyzed by endonucleases in the presence of Co-phthalocyanine complex [CoPc(COONa)₈] containing eight carboxyl groups at the periphery of the ligand was studied. It was shown that the efficiency of enzyme catalysis decreases in the presence of the metal complex for both endonucleases. By addition of a 100-fold excess of Co-phthalocyanine complex with respect to DNA duplex the initial rate of substrate hydrolysis by restriction endonuclease SsoII is observed to decrease twice. An equimolar ratio of the metal complex and hybrid duplex leads to essentially complete inhibition of RNA cleavage by RNase H from E. coli. The inhibition of catalytic activity of enzymes recognizing the double-stranded nucleic acids in the presence of Co-phthalocyanine complex is assumed to be caused by the ability of the latter to interact with DNA, RNA, and DNA--RNA duplexes.

---

KEY WORDS: Co-phthalocyanine complex, DNA duplex, DNA--RNA duplex, restriction endonuclease SsoII, RNase H

---