Single-molecule microscopy reveals new insights into nucleotide selection by DNA polymerase I.
The mechanism by which DNA polymerases achieve their extraordinary accuracy has been intensely studied because of the linkage between this process and mutagenesis and carcinogenesis. Here, we have used single-molecule fluorescence microscopy to study the process of nucleotide selection and exonuclease action. Our results show that the binding of Escherichia coli DNA polymerase I (Klenow fragment) to a primer-template is stabilized by the presence of the next correct dNTP, even in the presence of a large excess of the other dNTPs and rNTPs. These results are consistent with a model where nucleotide selection occurs in the open complex prior to the formation of a closed ternary complex. Our assay can also distinguish between primer binding to the polymerase or exonuclease domain and, contrary to ensemble-averaged studies, we find that stable exonuclease binding only occurs with a mismatched primer terminus.
Department of Chemistry, Wayne State University, Detroit, MI, USA.
Radoslaw P
RP
Markiewicz
Kyle B
KB
Vrtis
David
D
Rueda
Louis J
LJ
Romano
D020137:Base Pair Mismatch; D020029:Base Pairing; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004256:DNA Polymerase I / Q000737:chemistry / Q000378:metabolism*; D017931:DNA Primers; D003854:Deoxyribonucleotides / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology; D005090:Exodeoxyribonucleases / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D008856:Microscopy, Fluorescence / Q000379:methods; D012265:Ribonucleotides / Q000378:metabolism; D012965:Sodium Chloride / Q000737:chemistry; D055672:Static Electricity; D013698:Templates, Genetic
D017931:DNA Primers; D003854:Deoxyribonucleotides; D012265:Ribonucleotides; D012965:Sodium Chloride; D004247:DNA; D004256:DNA Polymerase I; D005090:Exodeoxyribonucleases