High resolution crystal structure of domain I of the Saccharomyces cerevisiae homing endonuclease PI-SceI

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Abstract
The homing endonuclease PI‐SceI from Saccharo myces cerevisiae consists of two domains. The protein splicing domain I catalyzes the excision of the mature endonuclease (intein) from a precursor protein and the religation of the flanking amino acid sequences (exteins) to a functional protein. Furthermore, domain I is involved in binding and recognition of the specific DNA substrate. Domain II of PI‐SceI, the endonuclease domain, which is structurally homologous to other homing endonucleases from the LAGLIDADG family, harbors the endonucleolytic center of PI‐SceI, which in vivo initiates the homing process by introducing a double‐strand cut in the ∼35 bp recognition sequence. At 1.35 Å resolution, the crystal structure of PI‐SceI domain I provides a detailed view of the part of the protein that is responsible for tight and specific DNA binding. A geometry‐based docking of the 75° bent recognition sequence to the full‐length protein implies a conformational change or hinge movement of a subdomain of domain I, the tongs part, that is predicted to reach into the major groove near base pairs +16 to +18.