Bacterial DNA Methyltransferases

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9983125ReichEnzymes that alter the structure of DNA perform functions that are essential for life. DNA methyltransferases expand the information content of DNA by modifying specific adenines and cytosines. DNA methylation is the most common form of epigenetic control of gene expression and occurs in organisms ranging from bacteria to man. This is an essential modification whose mechanism is not completely understood. This project addresses this topic using bacterial enzymes in an attempt to understand the molecular basis of sequence-specific DNA modification. DNA methylases bend the DNA and flip out their target bases prior to catalysis. This project builds on recent discoveries funded by NSF and conducted in this PI's laboratory, that allow the tracking of both DNA bending and base flipping in real time. This research area, the study of conformational mechanisms of DNA modifying enzymes, is only feasible through the use of several kinetic and spectroscopic methods pioneered by the PI and in conjunction with collaborators. Understanding the underlying mechanisms of such conformational changes is critical if we are to appreciate how such enzymes discriminate among DNA sequences, and carry out their particular chemistries. Most importantly, other methods such as x-ray crystallography do not provide the necessary quantitative and functional insights since they cannot provide dynamic information. This information is clearly important to gain an understanding of conformational transitions to enzyme specificity. The insights provided by this research should have implications for understanding the mechanism of action of other enzymes such as those involved in DNA repair since many of them also appear to use similar conformational mechanisms, as revealed by other investigators using methods similar to those pioneered here.