• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Infection and immunity >Characterization of the Catalytic Domain ofClostridium novyi Alpha-Toxin
【24h】

Characterization of the Catalytic Domain ofClostridium novyi Alpha-Toxin

机译：诺维梭菌α-毒素催化域的表征

获取原文
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Clostridium novyi alpha-toxin belongs to the family of large clostridial cytotoxins which act on cells through the modification of small GTP-binding proteins. We present here an analysis of the catalytic domain of alpha-toxin. A NH2-terminal 551-amino-acid fragment, α551, was found to contain the full enzyme activity of the holotoxin, whereas a slightly shortened fragment encompassing 509 amino acids showed no detectable enzyme activity. Further characterization of the enzymatically active fragment α551 revealed a substrate specificity for both UDP–N-acetylglucosamine and UDP-glucose. A Michaelis-Menten constant of 17 μM was determined for the substrate UDP–N-acetylglucosamine, while that for UDP-glucose was about 20 times higher, indicating a weaker affinity of the toxin for the latter substrate. Mutation of the aspartic acids of a conserved motif DXD within α551 reduced enzyme activity >700-fold and inhibited cytotoxicity after microinjection in cells. Inhibition of enzyme activity of the DXD mutant could be partially overcome by increased concentrations of manganese ions, suggesting the involvement of these aspartic acids in Mn2+ binding. By construction of chimeras of enzymatically active fragments of C. sordelliilethal toxin and C. novyi alpha-toxin, we located the region involved in nucleotide-sugar specificity to amino acids 133 through 517.
机译：新孢梭菌α毒素属于大梭菌细胞毒素家族，可通过修饰小的GTP结合蛋白作用于细胞。我们在这里介绍的α毒素的催化域的分析。发现NH 2 末端的551个氨基酸片段α551具有全毒素的全部酶活性，而略微缩短的包含509个氨基酸的片段则没有可检测的酶活性。酶活性片段α551的进一步表征揭示了对UDP- N -乙酰氨基葡萄糖和UDP-葡萄糖的底物特异性。对于底物UDP- N -乙酰氨基葡萄糖，测定的Michaelis-Menten常数为17μM，而对于UDP-葡萄糖，其Michaelis-Menten常数大约高20倍，表明毒素对后一种底物的亲和力较弱。守恒基序DXD的天冬氨酸突变在α551内降低了酶活性> 700倍，并在细胞显微注射后抑制了细胞毒性。锰离子浓度的增加可以部分克服DXD突变体对酶活性的抑制作用，表明这些天冬氨酸参与了Mn 2 + 结合。通过构建嵌合酶的 C酶活性片段。 Sordellii致死毒素和C。 novyi α-毒素，我们将核苷酸糖的特异性区域定位在133至517位氨基酸之间。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号