Restriction barrier composed of an extracellular nuclease and restriction endonuclease in the unicellular cyanobacterium Microcystis sp. |
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Authors: | Isamu Takahashi Daisuke Hayano Munehiko Asayama Futagami Masahiro Masanori Watahiki Makoto Shirai |
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Institution: | Division of Biotechnology, School of Agriculture, Ibaraki University, Ami, Ibaraki 300-03, Japan; Enzymological Research Laboratory, Nippon Gene Co. Ltd, Toyama 930, Japan |
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Abstract: | Abstract The unicellular cyanobacterium Microcystis aeruginosa K-81 has two types of restriction barrier, an extracellular nuclease and sequence-specific endonuclease. The nuclease was detected in the culture supernatant and it was easily released from the cells by washing with water or buffer containing Triton X-100. This nuclease was identified as a polypeptide of about 28 kDa that digested covalently closed circular and linear double-stranded DNAs, including chromosomal DNA from M. aeruginosa K-81. Among another 13 Microcystis strains examined, 3 produced an extracellular nuclease. Furthermore, M. aeruginosa K-81 contained two sequence-specific endonucleases, Mae K81I and Mae K81II, which were isoschizomers of Sp /I and Sau 96I, respectively. |
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Keywords: | Restriction endonuclease Extracellular nuclease Cyanobacteria Microcystis Sp/I isoschizomer Sau96I isoschizomer |
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