ISOLATION AND CHARACTERIZATION OF A NEWLY IDENTIFIED TYPE-II RESTRICTION-ENDONUCLEASE FROM A LOCAL STREPTOMYCES SP. IN TAIWAN

Streptomyces chusanensis ZS-2, isolated from a soil sample in Chusan i n Taiwan, was found to produce a new Type II restriction endonuclease. This restriction enzyme was designated as SchI. The purified enzyme w as characterized as having a subunit mol wt of 28 kDa, and was apparen tly free from exonuclease activities. It cleaves the phosphodiester bo nd between the fourth C and the fifth G on the 5'-CCGCGG-3' sequence o f DNAs, leaving a 2-nucleotide protruding end at its 3' site. This dat a suggests that SchI is an isoschizomer of SacII. Ln addition, based o n the comparison between SchI and SacII regarding reaction parameters, it seems that SchI is a better choice of restriction enzyme for genet ic analysis and mapping.