CHAMPAIGN, Ill. Using an extremely sensitive measurement technique, researchers at the University of Illinois have found clear evidence that a lead-specific DNAzyme uses the lock and key reaction mechanism. In the presence of zinc or magnesium, however, the same DNAzyme uses the induced fit reaction mechanism, similar to that used by ribozymes.
The lock and key mechanism explains why this particular lead-specific DNAzyme makes such a sensitive and selective sensor, said U. of I. chemistry professor Yi Lu, a corresponding author of a paper accepted for publication in Nature Chemical Biology, and posted on the journals Web site.
Understanding the relationship between conformational change and reaction is important in obtaining deeper insight into how DNAzymes work and for designing more efficient sensors, said Lu, who also is a researcher in the universitys department of biochemistry, the Beckman Institute, and the Center of Advanced Materials for the Purification of Water with Systems.
In the early 1980s, RNA molecules that can catalyze enzymatic reactions were discovered and named ribozymes. This discovery was followed by demonstrations in the 1990s that DNA also can act as enzymes, termed deoxyribozymes or DNAzymes.
With only four nucleotides as building blocks, versus 20 in proteins, nucleic acid enzymes may need to recruit cofactors (helper molecules) to perform some functions. Metal ions are a natural choice, and indeed most nucleic acid enzymes require metal ions for function under physiological conditions (and therefore are called metalloenzymes).
Metalloenzymes use various modes for functions for which metal-dependent conformational change (induced fit) is required in some cases but not in others (lock and key). In contrast, most ribozymes require conformation change that almost always precedes the enzyme reactions.
Using an extremely sensitive measurement technique called single-molecule fluorescence resonance energy transfer,
|Contact: James E. Kloeppel|
University of Illinois at Urbana-Champaign