Crystal structure of the Holliday junction resolving enzyme T7 endonuclease I

• Published in: Nature structural & molecular biology Vol. 8; no. 1; pp. 62 - 67
• Main Authors: Phillips, Simon E.V, Hadden, Jonathan M, Convery, Máire A, Déclais, Anne-Cécile, Lilley, David M.J
• Format: Journal Article
• Language: English
• Published: United States Nature Publishing Group 01.01.2001
• Subjects: Amino Acid Sequence; Amino acids; Bacterial Proteins - chemistry; Bacteriophage T7 - enzymology; Binding Sites; Conserved Sequence; Crystallography, X-Ray; Deoxyribonuclease I - chemistry; Deoxyribonuclease I - metabolism; Dimerization; DNA - genetics; DNA - metabolism; DNA Restriction Enzymes - chemistry; Endodeoxyribonucleases - chemistry; Endodeoxyribonucleases - genetics; endonuclease I; Escherichia coli Proteins; Models, Molecular; Molecular Sequence Data; Mutation; Phage T7; Protein Structure, Secondary; Recombination, Genetic; Substrate Specificity
• ISSN: 1072-8368; 1545-9993; 2331-365X; 1545-9985
• DOI: 10.1038/83067

We have solved the crystal structure of the Holliday junction resolving enzyme T7 endonuclease I at 2.1 Å resolution using the multiwavelength anomalous dispersion (MAD) technique. Endonuclease I exhibits strong structural specificity for four-way DNA junctions. The structure shows that it forms a symmetric homodimer arranged in two well-separated domains. Each domain, however, is composed of elements from both subunits, and amino acid side chains from both protomers contribute to the active site. While no significant structural similarity could be detected with any other junction resolving enzyme, the active site is similar to that found in several restriction endonucleases. T7 endonuclease I therefore represents the first crystal structure of a junction resolving enzyme that is a member of the nuclease superfamily of enzymes.