镉胁迫下蚯蚓金属硫蛋白氧化修饰的研究

Oxidative Modification of Metallothionein in Earthworm under Cd Stress

金属硫蛋白(MT)是生物体内的一类富含巯基(—SH)的蛋白,在细胞氧化还原调控和重金属解毒等方面具有重要作用.MT的—SH可以络合重金属,同时对氧化作用很敏感,重金属胁迫产生的活性氧物质(ROS)可以将其氧化成二硫键(S—S).为揭示镉(Cd)对蚯蚓MT的—SH含量及其氧化修饰的影响,将蚯蚓放入Cd浓度为0、100、300mg·kg-1的黄棕壤中胁迫21天,通过SBD-F标记和高效液相色谱(HPLC)结合的方法测定MT中—SH和S—S的含量.结果显示,随着Cd浓度的增加,蚯蚓体内的—SH和S—S含量均逐渐增加,但S—S所占比例降低.这说明Cd诱导了蚯蚓体内MT合成,并且诱导量随着Cd胁迫的增强而增加,但—SH的氧化修饰程度有所下降.

Metallothionein （MT）is a protein with high content of sulfhydryl（—SH）group in organisms. It plays important roles in cell-redox regulation and heavy-metal detoxication. The—SH group of MT can bind heavy metals and it is very sensitive to oxidation. It can be oxidized into disulfide（S—S）by reactive oxygen substances（ROS） which are generated under heavy metal stress. To reveal the effects of Cd on the content of—SH and its oxidative modification, earthworms were exposed to the yellow brown soil which concentrations of Cd are 0, 100, and 300mg·kg-1 for 3 weeks. The—SH groups in the earthworm were labeled using a fluorophore, ammonium-7-fluorobenz-2-oxa-1,3-diazole-4-sulfonate（SBD-F）, and then quantified with high-performance liquid chromatography（HPLC）. Disulfide bonds were first reduced and then analyzed with the above procedures. Results show that the amounts of —SH and S—S increased with the Cd additions, suggesting that the MT synthesis was induced under the exposure of Cd. However, the decreased proportion of S—S indicats that the extent of MT oxidative modification declined.