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Configuration of the catalytic GIY-YIG domain of intron endonuclease I-TevI: coincidence of computational and molecular findings

1999; Oxford University Press; Volume: 27; Issue: 10 Linguagem: Inglês

10.1093/nar/27.10.2115

1362-4962

Joseph C. Kowalski, Marlene Belfort, Michelle Stapleton, Mathias Holpert, John T. Dansereau, Shmuel Pietrokovski, Steven M. Baxter, Victoria Derbyshire,

CRISPR and Genetic Engineering

I-TevI is a member of the GIY-YIG family of homing endonucleases. It is folded into two structural and functional domains, an N-terminal catalytic domain and a C-terminal DNA-binding domain, separated by a flexible linker. In this study we have used genetic analyses, computational sequence analysis and NMR spectroscopy to define the configuration of the N-terminal domain and its relationship to the flexible linker. The catalytic domain is an α/β structure contained within the first 92 amino acids of the 245-amino acid protein followed by an unstructured linker. Remarkably, this structured domain corresponds precisely to the GIY-YIG module defined by sequence comparisons of 57 proteins including more than 30 newly reported members of the family. Although much of the unstructured linker is not essential for activity, residues 93–116 are required, raising the possibility that this region may adopt an alternate conformation upon DNA binding. Two invariant residues of the GIY-YIG module, Arg27 and Glu75, located in α-helices, have properties of catalytic residues. Furthermore, the GIY-YIG sequence elements for which the module is named form part of a three-stranded antiparallel β-sheet that is important for I-TevI structure and function.