RecB-family nuclease motif in the Type I restriction endonuclease EcoR124I

• Published in: Nucleic acids research Vol. 36; no. 12; pp. 3939 - 3949
• Main Authors: Šišáková, Eva, Stanley, Louise K, Weiserová, Marie, Szczelkun, Mark D
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01-07-2008; Oxford Publishing Limited (England)
• Subjects: Amino Acid Motifs; Amino Acid Sequence; Amino Acid Substitution; Deoxyribonucleases, Type I Site-Specific - chemistry; Deoxyribonucleases, Type I Site-Specific - genetics; Deoxyribonucleases, Type I Site-Specific - metabolism; DNA - metabolism; Exodeoxyribonuclease V - chemistry; Kinetics; Molecular Sequence Data; Mutagenesis; Nucleic Acid Enzymes; Protein Subunits - chemistry; Protein Transport; Sequence Alignment
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/gkn333

The Type I restriction-modification enzyme EcoR124I is an ATP-dependent endonuclease that uses dsDNA translocation to locate and cleave distant non-specific DNA sites. Bioinformatic analysis of the HsdR subunits of EcoR124I and related Type I enzymes showed that in addition to the principal PD-(E/D)xK Motifs, I, II and III, a QxxxY motif is also present that is characteristic of RecB-family nucleases. The QxxxY motif resides immediately C-terminal to Motif III within a region of predicted α-helix. Using mutagenesis, we examined the role of the Q and Y residues in DNA binding, translocation and cleavage. Roles for the QxxxY motif in coordinating the catalytic residues or in stabilizing the nuclease domain on the DNA are discussed.