The I-CeuI endonuclease: purification and potential role in the evolution of Chlamydomonas group I introns.
During genetic crosses between the interfertile green algae Chlamydomonas eugametos and Chlamydomonas moewusii, the I-CeuI endonuclease encoded by the fifth group I intron (CeLSU.5) in the C. eugametos chloroplast large subunit rRNA gene mediates the mobility of this intron by introducing a double-strand break near the insertion site of the intron in the corresponding C. moewusii intronless allele. To characterize the biochemical properties of this endonuclease, we have purified I-CeuI and determined the optimal reaction conditions for cleavage. I-CeuI activity is maximal at 50 degrees C, pH 10.0, 2.5 mM MgCl2 and in the absence of NaCl. Unlike the well-characterized I-SceI endonuclease, I-CeuI remains stable following preincubation in the absence of substrate. We discuss the role that homing endonucleases may have played in the evolution of Chlamydomonas chloroplast group I introns.
Marshall
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P
Département de Biochimie, Faculté des Sciences et de Génie, Université Laval, Québec, Canada.
Davis
T B
TB
Lemieux
C
C
D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002696:Chlamydomonas / Q000201:enzymology / Q000235:genetics*; D002736:Chloroplasts; D004706:Endodeoxyribonucleases / Q000302:isolation & purification* / Q000378:metabolism; D007438:Introns; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011489:Protein Denaturation; D013696:Temperature
D004706:Endodeoxyribonucleases; C071132:endodeoxyribonuclease I-CeuI