MECHANISM OF ACTION OF ESCHERICHIA-COLI ENDONUCLEASE-III
MECHANISM OF ACTION OF ESCHERICHIA-COLI ENDONUCLEASE-III
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DOI：
10.1021/bi00399a027
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发表时间：
1987-12-15
期刊：
影响因子：
2.9
通讯作者：
WALLACE, SS
中科院分区：
文献类型：
--
作者：
KOW, YW;WALLACE, SS
从大肠杆菌中分离到的核酸内切酶III具有N-糖基酶和脱嘌呤/脱嘧啶(AP)内切酶活性。缺口试验表明，当DNA中含有胸腺嘧啶二醇作为底物时，该酶表现出对I型DNA的偏好。当DNA松弛时，或者当损伤类型改变为尿素残留物或AP位点时，这种偏好被减少或消除。当以含尿素的DNA为底物时，N-糖基酶/AP内切酶的联合活性比单独的AP内切酶活性高至少10倍。以含胸腺嘧啶二醇的DNA为底物时，N-糖基酶/AP内切酶活力约为AP酶活力的2倍。然而，当以含胸腺嘧啶乙二醇或尿素的DNA为底物时，没有留下无嘌呤中心。此外，当以AP DNA为底物时，镁有选择性地抑制内切酶III的活性，而当DNA中含有尿素或胸腺嘧啶二醇时，镁对酶III的活性没有影响。这些数据表明，核酸内切酶III的N-糖基酶和AP内切酶活性都位于同一分子上或存在非常紧密的联系，并且这些活性是协同作用的，N-糖基酶反应先于AP内切酶反应。
Endonuclease III isolated from Escherichia coli has been shown to have both N-glycosylase and apurinic/apyrimidinic (AP) endonuclease activities. A nicking assay was used to show that the enzyme exhibited a preference for form I DNA when DNA containing thymine glycol was used as a substrate. This preference was reduced or eliminated either when the DNA was relaxed or when the type of damage was altered to urea residues or AP sites. The combined N-glycosylase/AP endonuclease activity was at least 10-fold higher than the AP endonuclease activity alone when urea-containing DNA was used as a substrate as compared to AP DNA. When DNA containing thymine glycol was used as a substrate, the combined N-glycosylase/AP endonuclease activity was about 2-fold higher than the AP endonuclease activity. Yet, when DNA containing thymine glycol or urea was used as substrate, no apurinic sites remained. Furthermore, magnesium selectively inhibited endonuclease III activity when AP DNA was used as a substrate but had no effect when DNA containing either urea or thymine glycol was used as substrate. These data suggest that both the N-glycosylase and AP endonuclease activities of endonuclease III reside on the same molecule or are in very tight association and that these activities act in concert, with the N-glycosylase reaction preceding the AP endonuclease reaction.