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C-terminal domain of type IIs restriction endonuclease BfiI and similar proteins C-terminal domain of a novel type IIs restriction endonuclease BfiI and similar proteins. Type II restriction endonucleases are components of restriction modification (RM) systems that protect bacteria and archaea against invading foreign DNA. They usually function as homodimers or homotetramers that cleave DNA at defined sites of 4 to 8 bp in length, and they require Mg2+, not ATP or GTP, for catalysis. Unlike all other restriction enzymes known to date, BfiI is unique in cleaving DNA at fixed positions downstream of an asymmetric sequence in the absence of Mg2+. BfiI consists of two discrete domains with distinct functions: an N-terminal catalytic domain with non-specific nuclease activity and dimerization function that is more closely related to Nuc, an EDTA-resistant nuclease from the phospholipase D (PLD) superfamily; and a C-terminal domain that specifically recognizes its target sequences, 5'-ACTGGG-3'. BfiI presumably evolved through domain fusion of a DNA recognition domain to the catalytic Nuc-like domain from the PLD superfamily. BfiI forms a functionally active homodimer which has two DNA-binding surfaces located at the C-terminal domains but only one active site, located at the dimer interface between the two N-terminal catalytic domains. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",