Bielecki J
Institute of Microbiology, Warsaw University, Poland.
Acta Microbiol Pol. 1994;43(3-4):279-89.
The single amino acid substitutions were created in the C-terminal region of listeriolysin O. Mutations cys484 to Ala and Ser showed a close relationship between surface activity of LLO and presence of cysteine in this polipeptide. We demonstrated that Cys484 is necessary for surface haemolytic activity. LLO with Cys484 is strongly connected to the surface of the cell but LLO Ala484 or Ser484 is easy removed by the washing. Listeriolysins O secreted by the mutants were active at low pH and inhibited by cholesterol. Mutated hemolysin was still active at high pH without cysteine in reaction mixture whereas wild hemolysin was not. Surface haemolytic activity was blocked in Ala484 strain at high pH. The finding that mutants Ala484 and Ser484 have changed surface activity suggests that cysteine in LLO may play a significant role for surface haemolytic activity necessary in late stages of Listeria monocytogenes cell cycle.
在溶血素O的C末端区域产生了单氨基酸取代。半胱氨酸484突变为丙氨酸和丝氨酸表明溶血素O的表面活性与该多肽中半胱氨酸的存在密切相关。我们证明半胱氨酸484对于表面溶血活性是必需的。含有半胱氨酸484的溶血素O与细胞表面紧密相连，但丙氨酸484或丝氨酸484的溶血素O很容易被洗涤去除。突变体分泌的溶血素O在低pH下有活性且受胆固醇抑制。在反应混合物中没有半胱氨酸的情况下，突变的溶血素在高pH下仍有活性，而野生型溶血素则没有。在高pH下，丙氨酸484菌株的表面溶血活性被阻断。丙氨酸484和丝氨酸484突变体表面活性发生改变这一发现表明，溶血素O中的半胱氨酸可能对单核细胞增生李斯特菌细胞周期后期所需的表面溶血活性起重要作用。
