nisin Z铰链区电荷突变体抑菌性的研究

以含nisZ基因的质粒pHJ201为模板,对乳链菌肽铰链区进行定点突变,并以pMG36e为载体,转入受体菌L.lactis NZ9800进行表达,研究不同电荷铰链区突变体的特性及结构。结果表明,9个突变体中除N 20En is in Z,M21E nisinZ和K22E n is in Z失去抑菌活性外,其余突变体的抑菌活性均有下降;N20K nisinZ和M21KnisinZ突变体的抑菌谱发生了变化,其对革兰氏阴性菌沙门氏菌、志贺氏菌和假单胞菌均有抑菌活性。CD谱表明,在波长210~220 nm区,N 20K nisinZ和M21KnisinZ的-αhelix值均较野生型nisinZ略有提高。

Inhibition of nisin Z mutants with charge in hinge region

To study the effect of charge in hinge region on the relation between structure and function, we changed certain amino acid of hinge region by performing site-directed mutagenesis with nis Z gene. The results showed that the antimicrobial activities of nine mutants decreased ,while N20E nisin Z,M21E nisin Z and K22E nisin Z,introducing negative charge residue into hinge region, nearly lost the activity. Compared with wild-type nisin Z,mutant N20K nisin Z and M21K nisin Z displayed antimicrobial activity against gram-negative Shigella, Pseudomonas and Salmonella. Meanwhile, the data of N20K nisin Z and M21K nisin Z CD spectrum showed similarities to that of wild-type nisin Z in secondary structures. The small difference in intensity in the 210-220 nm region between the CD spectra of the wild-type and those of the mutants showed subtle changes in the structural composition of nisin Z,