Structure and Function of an RNA-Reading Thermostable DNA Polymerase

摘要

The high substrate specificity of DNA-dependent DNA polymerases is essential for the stability of the genome as well as many biotechnological applications. The discrimination between ribo- and deoxyribonucleotides and between RNA and DNA, particularly in cells, is fundamental since the concentration of ribo moieties by far exceeds that of deoxyribo analogues. Although the selection mechanisms for the incorporation of nucleotides have been investigated intensively for DNA and RNA polynierases, much less is known on how DNA-dependent DNA polymerases discriminate between the different nucleic acid templates (DNA versus RNA). Some viral DNA polymerases (e.g. reverse transcriptases) can utilize both DNA and RNA as a template for nucleic acid synthesis. Crystal-structure analysis of these enzymes, complexed either to an RNA or DNA template, have contributed significantly to our understanding of this process.However, similar structural data of DNA-dependent DNA polymerases that have a poor propensity to process RNA templates are lacking, presumably because the crystallization is hampered by the formation of unstable complexes that leads to structural heterogeneity.