1a74

I-PPOL HOMING ENDONUCLEASE/DNA COMPLEX

spinqualitylabelsall models 1a74, resolution 2.20Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1a74 is a 4 chain structure. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: ZN Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [PPO1_PHYPO] Mediates the homing of a group I intron in the ribosomal DNA. Makes a four-base staggered cut in its ribosomal DNA target sequence. Publication Abstract from PubMed Homing endonucleases are a diverse collection of proteins that are encoded by genes with mobile, self-splicing introns. They have also been identified in self-splicing inteins (protein introns). These enzymes promote the movement of the DNA sequences that encode them from one chromosome location to another; they do this by making a site-specific double-strand break at a target site in an allele that lacks the corresponding mobile intron. The target sites recognized by these small endonucleases are generally long (14-44 base pairs). Four families of homing endonucleases have been identified, including the LAGLIDADG, the His-Cys box, the GIY-YIG and the H-N-H endonucleases. The first identified His-Cys box homing endonuclease was I-PpoI from the slime mould Physarum polycephalum. Its gene resides in one of only a few nuclear introns known to exhibit genetic mobility. Here we report the structure of the I-PpoI homing endonuclease bound to homing-site DNA determined to 1.8 A resolution. I-PpoI displays an elongated fold of dimensions 25 x 35 x 80 A, with mixed alpha/beta topology. Each I-PpoI monomer contains three antiparallel beta-sheets flanked by two long alpha-helices and a long carboxy-terminal tail, and is stabilized by two bound zinc ions 15 A apart. The enzyme possesses a new zinc-bound fold and endonuclease active site. The structure has been determined in both uncleaved substrate and cleaved product complexes. DNA binding and cleavage by the nuclear intron-encoded homing endonuclease I-PpoI.,Flick KE, Jurica MS, Monnat RJ Jr, Stoddard BL Nature. 1998 Jul 2;394(6688):96-101. PMID:9665136 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Endonuclease

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