nisin Z铰链区电荷突变体抑菌性的研究

Inhibition of nisin Z mutants with charge in hinge region

以含nis Z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N20E nisin Z,M21E nisin Z和K22E nisin Z失去抑菌活性外,其余突变体的抑菌活性均有下降;N20K nisin Z和M21K nisin Z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,N20K nisin Z和M21K nisin Z的α-helix值均较野生型nisin Z略有提高.

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,