Francis S H, Colbran J L, McAllister-Lucas L M, Corbin J D
Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0615.
J Biol Chem. 1994 Sep 9;269(36):22477-80.
cGMP-binding cGMP-specific phosphodiesterase (cG-BPDE) binds tightly to a Zn(2+)-chelate column (Francis, S. H., and Corbin, J. D. (1988) Methods Enzymol. 159, 722-729). Using three different approaches, Zn2+ is now shown to bind to cG-BPDE, and the Kd is determined to be approximately 0.5 microM, with a binding stoichiometry of approximately 3 mol of Zn2+/mol of monomer. A similar concentration range of Zn2+ (0.05-1 microM Zn2+) also supports phosphodiesterase (PDE) catalytic activity. The Zn2+ binding to cG-BPDE is not diminished by, nor is catalysis supported by, relatively high concentrations of Cu2+, Cd2+, Ca2+, or Fe2+. Neither cGMP nor 3-isobutyl-1-methylxanthine affects Zn2+ binding under the conditions used. Mn2+, Co2+, or Mg2+ supports catalysis, but only at significantly higher concentrations (4-, 15-, and 250-fold, respectively) than that required for Zn2+. Two tandem amino acid sequences, which are conserved in the catalytic domains of all characterized mammalian PDEs, resemble the single sequence motif that has been shown to coordinate Zn2+ in the catalytic sites of Zn2+ hydrolases such as thermolysin.