Characterization of RecA424 and RecA670 proteins from
放射線抵抗性細菌デイノコッカス・ラジオデュランスRecA424及びRecA670の特性
佐藤 勝也; 鳴海 一成; 菊地 正博; 北山 滋; 柳沢 忠*; 山本 和生; 渡辺 宏
Sato, Katsuya; Narumi, Issei; Kikuchi, Masahiro; Kitayama, Shigeru; Yanagisawa, Tadashi*; Yamamoto, Kazuo; Watanabe, Hiroshi
これまでデイノコッカス・ラジオデュランスRecAは,大腸菌とは異なり特別な機能を有しているのではないかと考えられてきた。本論文ではラジオデュランスの野生型及び2種類の変異型RecAを解析し,ラジオデュランスRecAが大腸菌RecAと同等の機能を有していること、当該菌の放射線抵抗性にはRecAによるDNA組換え活性よりも、co-protease活性の方がより重要な役割を担っていることを示した。
RecA protein is considered to be the most important participant in the radiation resistance of . We identified a new mutation () in the DNA-repair deficient mutant strain KI696, the phenotype of which is remarkably different from mutant strain rec30 carrying . In vitro, neither RecA424 nor RecA670 could promote DNA strand exchange, indicating that both RecA424 and Rec670 are defective in recombination activity. RecA424 promoted the autocleavage reaction of LexA in vitro, whereas RecA670 did not. The LexA level in KI696 was decreased following -irradiation. However, the LexA level in strain rec30 was constant irrespective of irradiation. These results indicate that RecA424 retains co-protease activity, whereas RecA670 does not. While strain rec30 is extremely radiation sensitive, strain KI696 is only slightly sensitive. Together, these observations suggest that the co-protease activity rather than the recombination activity of RecA contributes to the radiation resistance in .