Study of the Mechanism of Action of p-Chloromercuribenzoate on Endonuclease from the Bacterium Serratia marcescens

M. N. Filimonova^1*, V. P. Gubskaya², I. A. Nuretdinov², M. J. Benedik³, N. A. Cherepanova¹, and I. B. Leshchinskaya¹

¹Department of Microbiology, Kazan State University, ul. Kremliovskaya 18, Kazan, 420008 Russia; E-mail: maria.filimonova@ksu.ru

²Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center, Russian Academy of Sciences, ul. Arbuzova 8, Kazan, 420088 Russia; fax: (2-843) 752-253; E-mail: in@iopc.ksn.ru

³Department of Biochemical and Biophysical Sciences, University of Houston, Houston, TX 77204-5934, USA; fax: (713) 743-8351; E-mail: benedik@uh.edu

^* To whom correspondence should be addressed.

Received May 29, 2000; Revision received August 29, 2000

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The mechanism of action of p-chloromercuribenzoate (PCMB) on Serratia marcescens nuclease was investigated. The analysis showed that PCMB forms complexes with DNA. Binding of C₇H₅O₂Hg⁺ to DNA changes the secondary structure of the DNA. These changes alter the enzymatic activity of S. marcescens nuclease, which was previously found to be sensitive to the secondary structure of the substrates. The nuclease activity was either suppressed or stimulated in the presence of PCMB depending on the C₇H₅O₂Hg⁺ to nucleotide equivalent ratio. Binding of C₇H₅O₂Hg⁺ to DNA did not form an abortive enzyme-substrate complex. Binding of Mg²⁺ to the C₇H₅O₂Hg-DNA complex caused appropriate changes in secondary structure of the substrate. Since Mg²⁺ and C₇H₅O₂Hg⁺, though differing in the type of metal cation, are similar in their mechanisms of influence on enzymatic activity of S. marcescens nuclease, the identity of other metal-containing effectors in their mechanism of action on Serratia marcescens nuclease is assumed.

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KEY WORDS: endonuclease, Serratia marcescens, CD, PCMB, DNA

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