猪链球菌7型噬菌体裂解酶Ly7917催化域的裂菌活性

Catalytic domain of endolysin Ly7917 harbored in lysogenic phage of Streptococcus suis 7

摘要:

【目的】揭示链球菌噬菌体裂解酶Ly7917催化域CHAP的核心功能域，为进一步改造裂解酶提供理论依据。【方法】通过表达纯化分别从N端截短的Ly7917及从C端截短的LyCHAP各蛋白，基于平板裂解试验和浊度递减试验，比较各截短蛋白之间的活性差异，以及添加Ca2+后各蛋白的活性变化。【结果】发现催化域蛋白LyCHAP与Ly7917全酶的活性差异不显著，LyCHAP的N端序列对其活性影响较大，不宜截短；而C端依次截短后，活性逐渐降低。C端截短20个氨基酸的LyCHAP1?130，在添加1 mmol/L Ca2+后活性最强。【结论】Ly7917催化域CHAP的核心功能域为1?130 aa，推测其具有Ca2+结合区域，并发现LyCHAP1?130在Ca2+参与下裂菌活性可媲美Ly7917全酶。预示着LyCHAP1?130可以替代全酶应用于之后的临床试验。

Abstract:

[Objective] We focused on finding out the active area of catalytic domain of endolysin Ly7917 against Streptococcus suis, consequently helpful for Ly7917 modification. [Methods] A group peptides truncated from N-terminal of Ly7917 or C-terminal of LyCHAP were expressed and compared with original Ly7917 and LyCHAP of the catalytic activity by plate lysis assay and turbidity decrease assay, even the situation with addition of Ca2+. [Results] LyCHAP showed excellent catalytic activity as well as the full-length Ly7917. Truncated Ly7917 from N-terminal showed no catalytic activity. With the assistance of Ca2+, LyCHAP without 20 amino acids at C-terminal (LyCHAP1?130) could achieve the maximum catalytic effect even better than full-length LyCHAP. [Conclusion] Ca2+-dependent LyCHAP1?130 could be the potential alternative of Ly7917 for further clinic trials.