Structure of HinP1I endonuclease reveals a striking similarity to the monomeric restriction enzyme MspI.
HinP1I, a type II restriction endonuclease, recognizes and cleaves a palindromic tetranucleotide sequence (G/CGC) in double-stranded DNA, producing 2 nt 5' overhanging ends. Here, we report the structure of HinP1I crystallized as one protein monomer in the crystallographic asymmetric unit. HinP1I displays an elongated shape, with a conserved catalytic core domain containing an active-site motif of SDX18QXK and a putative DNA-binding domain. Without significant sequence homology, HinP1I displays striking structural similarity to MspI, an endonuclease that cleaves a similar palindromic DNA sequence (C/CGG) and binds to that sequence crystallographically as a monomer. Almost all the structural elements of MspI can be matched in HinP1I, including both the DNA recognition and catalytic elements. Examining the protein-protein interactions in the crystal lattice, HinP1I could be dimerized through two helices located on the opposite side of the protein to the active site, generating a molecule with two active sites and two DNA-binding surfaces opposite one another on the outer surfaces of the dimer. A possible functional link between this unusual dimerization mode and the tetrameric restriction enzymes is discussed.
Yang
Zhe
Z
Department of Biochemistry, Emory University School of Medicine 1510 Clifton Road, Atlanta, GA 30322, USA.
Horton
John R
JR
Maunus
Robert
R
Wilson
Geoffrey G
GG
Roberts
Richard J
RJ
Cheng
Xiaodong
X
D000595:Amino Acid Sequence; D001665:Binding Sites; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D019003:Deoxyribonuclease HpaII / Q000737:chemistry*; D015252:Deoxyribonucleases, Type II Site-Specific / Q000737:chemistry* / Q000378:metabolism; D019281:Dimerization; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D040681:Structural Homology, Protein
D004247:DNA; D019003:Deoxyribonuclease HpaII; D015252:Deoxyribonucleases, Type II Site-Specific; C037130:GCGC-specific type II deoxyribonucleases