| Summary: | 碩士 === 國立陽明大學 === 遺傳學研究所 === 90 === The terminal regions of the linear Streptomyces chromosomes are highly unstable, undergoing spontaneous large deletions of up to 2 Mb. Several deletion mutants of S. lividans contained circularized chromosomes, and could not be transformed by the linear plasmid SLP2. This suggested that these deletions contained at least one gene involved in the maintenance of the linear plasmids (designated lpm for linear plasmid maintenance). Because linear Streptomyces plasmids have 5’ covalently bound terminal protein, it is believed that chromosally encoded terminal protein gene (tpgL) might play a vital role in linear plasmid maintenance. Since the Lpm+ and Lpm- strains were tpgL+ and tpgL- , respectively, complementation test was performed to determine if tpgL was lpm. Insertion of a 4.5-kb fragment contains tpgL inserted into the chromosome or a mini-linear plasmid restored the Lpm+ phenotype to Lpm- host, this indicates that the 4.5-kb fragment contains the lpm function.
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