Structure and activity of the mitochondrial intron-encoded endonuclease, I-SceIV.
Starting with crude yeast mitochondria, the intron homing endonuclease, I-SecIV, was purified to near homogeneity. This highly purified enzyme differs from some other well-characterized yeast mitochondrial intron-encoded endonucleases in terms of its structure and DNA cleavage specificity. The enzyme is a heterodimer with a native molecular mass of 92 kDa. A small catalytic subunit (32 kDa) is probably encoded largely or entirely by intron 5 alpha of the cytochrome oxidase subunit I gene. A larger polypeptide subunit (60 kDa) may be a nuclear factor necessary for intron mobility. I-SceIV exhibits a low DNA sequence specificity as it cleaves a variety of DNA substrates. Analysis of kinetic parameters shows that the purified enzyme has a very high affinity for DNA and exhibits low turnover which may have implications for subsequent steps in the intron homing process.
Department of Chemistry, Auburn University, Alabama 36849-5312, USA. werneca@mail.auburn.edu
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D000818:Animals; D004247:DNA / Q000378:metabolism; D015252:Deoxyribonucleases, Type II Site-Specific / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D019281:Dimerization; D006801:Humans; D007438:Introns; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology*; D008970:Molecular Weight; D010957:Plasmids; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D013379:Substrate Specificity
D004247:DNA; C113482:endodeoxyribonuclease SceIV; D015252:Deoxyribonucleases, Type II Site-Specific