Send to:

Choose Destination
See comment in PubMed Commons below
Structure. 2010 Jun 9;18(6):734-43. doi: 10.1016/j.str.2010.03.009.

Unusual target site disruption by the rare-cutting HNH restriction endonuclease PacI.

Author information

  • 1Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N. A3-025, Seattle, WA 98109, USA.


The crystal structure of the rare-cutting HNH restriction endonuclease PacI in complex with its eight-base-pair target recognition sequence 5'-TTAATTAA-3' has been determined to 1.9 A resolution. The enzyme forms an extended homodimer, with each subunit containing two zinc-bound motifs surrounding a betabetaalpha-metal catalytic site. The latter is unusual in that a tyrosine residue likely initiates strand cleavage. PacI dramatically distorts its target sequence from Watson-Crick duplex DNA base pairing, with every base separated from its original partner. Two bases on each strand are unpaired, four are engaged in noncanonical A:A and T:T base pairs, and the remaining two bases are matched with new Watson-Crick partners. This represents a highly unusual DNA binding mechanism for a restriction endonuclease, and implies that initial recognition of the target site might involve significantly different contacts from those visualized in the DNA-bound cocrystal structures.

[PubMed - indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Elsevier Science Icon for PubMed Central
    Loading ...
    Write to the Help Desk