Devoret R, Pierre M, Moreau P L
Mol Gen Genet. 1983;189(2):199-206. doi: 10.1007/BF00337804.
In contrast to prophage lambda, wild-type prophage phi 80 was induced by UV-irradiation or thymine deprivation in recA430 mutants of E. coli K12. There was no induction of prophage phi 80 in two recombination-deficient mutants recA13 and recA99. Phage phi 80ind3, a non-inducible derivative in a rec+ was not induced in a recA430 lysogen. Two other lambdoid prophages were tested for UV-induction in recA430 lysogens: in common with lambda prophage, 434 was not induced whereas prophage 21 was induced in 1% of the cells. Induction of RecA430 protein synthesis was 30% of that observed in recA+ bacteria at 30 min of post-irradiation incubation, indicating that LexA repressor had been cleaved by RecA430 protease. In lexA1 recA430 and lexA1 recA+ bacteria, RecA protein synthesis was not amplified, yet, prophage phi 80 was fully induced. If phi 80cI repressor is inactivated by cleavage by RecA430 protease as is LexA repressor, RecA430 protease can inactivate all the molecules of phi 80cI repressor, its basal level being high enough in a recA430 lysogen. In such a lysogen, a fraction only of 21cI and LexA repressors are cleaved but no molecules of either lambda cI or 434cI repressor. We postulate that RecA430 protein has an altered pattern of recognition of repressor molecules and a cleavage efficiency which is more efficient the more remote is the repressor conformation from that of lambda repressor.
与λ原噬菌体不同，野生型φ80原噬菌体在大肠杆菌K12的recA430突变体中可被紫外线照射或胸腺嘧啶饥饿诱导。在两个重组缺陷突变体recA13和recA99中，φ80原噬菌体未被诱导。噬菌体φ80ind3是rec⁺中的一种不可诱导衍生物，在recA430溶原菌中也未被诱导。另外两种类λ原噬菌体在recA430溶原菌中进行了紫外线诱导测试：与λ原噬菌体一样，434未被诱导，而原噬菌体21在1%的细胞中被诱导。照射后培养30分钟时，RecA430蛋白合成的诱导水平是rec⁺细菌中观察到的30%，这表明LexA阻遏物已被RecA430蛋白酶切割。在lexA1 recA430和lexA1 recA⁺细菌中，RecA蛋白合成未被放大，但原噬菌体φ80被完全诱导。如果φ80cI阻遏物像LexA阻遏物一样被RecA430蛋白酶切割而失活，RecA430蛋白酶可以使所有的φ80cI阻遏物分子失活，其基础水平在recA430溶原菌中足够高。在这样的溶原菌中，只有一部分21cI和LexA阻遏物被切割，但λcI或434cI阻遏物分子均未被切割。我们推测，RecA430蛋白对阻遏物分子的识别模式发生了改变，其切割效率在阻遏物构象与λ阻遏物构象差异越大时越高。
