Structure-function investigation of a deoxyribozyme with dual chelatase and peroxidase activities
H.-W. Lee, D. J.-F. Chinnapen, and D. Sen
Department of Molecular Biology and Biochemistry,
Simon Fraser University, Burnaby, British Columbia V5A 1 S6, Canada
Abstract: PS2.M, an 18-nucleotide DNA molecule, has been shown
to be a dual enzyme for porphyrin metallation and, when complexed with
hemin, for peroxidation. To date, detailed information has not been
available on either the actively folded structure of PS2.M or on the
contribution of specific nucleotides within it toward the peroxidase
activity. Here, we report a variety of experiments that probe the structure
and function of PS2.M as well as of a number of point mutants of PS2.M.
Based on these experiments, a structural model for the folding of PS2.M
and the location of a functionally relevant hemin-binding site are proposed.
A key finding is that PS2.M, originally obtained by in vitro selection
from a random-sequence DNA library, is uniquely suited for its catalysis
of peroxidation; all point mutants examined showed significantly poorer
catalytic activity than PS2.M itself.
*Lecture presented at the symposium "Chemistry of nucleic acids", as part of the 39th IUPAC Congress and 86th Conference of the Canadian Society for Chemistry: Chemistry at the Interfaces, Ottawa, Canada, 10-15 August 2003. Other Congress presentations are published in this issue, pp. 1295-1603.
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