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| Content Provider | PubMed Central |
|---|---|
| Author | Nagahama, M. Okagawa, Y. Nakayama, T. Nishioka, E. Sakurai, J. |
| Abstract | Mutagenesis of H-68 or -148 in Clostridium perfringens alpha-toxin resulted in complete loss of hemolytic, phospholipase C, sphingomyelinase, and lethal activities of the toxin. These activities of the variant toxin at H-126 or -136 decreased by approximately 100-fold of the activities of the wild-type toxin. Mutation at H-46, -207, -212, or -241 showed no effect on the biological activities, indicating that these residues are not essential for these activities. The variant toxin at H-11 was not detected in culture supernatant and in cells of the transformant carrying the variant toxin gene. Wild-type toxin and the variant toxin at H-148 bound to erythrocytes in the presence of Ca2+; however, the variant toxins at H-68, -126, and -136 did not. Co2+ and Mn2+ ions stimulated binding of the variant toxin at H-68, -126, and -136 to membranes in the presence of Ca2+ and caused an increase in hemolytic activity. Wild-type toxin and the variant toxins at H-68, -126, and -136 contained two zinc atoms in the molecule. Wild-type toxin inactivated by EDTA contained two zinc atoms. These results suggest that wild-type toxin contains two tightly bound zinc atoms which are not coordinated to H-68, -126, and -136. The variant toxin at H-148 possessed only one zinc atom. Wild-type toxin and the variant toxin at H-148 showed [65Zn]2+ binding, but the variant toxins at H-68, -126, and -136 did not. Furthermore, [65Zn]2+ binding to wild-type toxin was competitively inhibited by unlabeled Zn2+, Co2+, and Mn2+. These results suggest that H-68, -126, and -136 residues bind an exchangeable and labile metal which is important for binding to membranes and that H-148 tightly binds one zinc atom which is essential for the active site of alpha-toxin. |
| Starting Page | 1179 |
| File Format | |
| ISSN | 10985530 |
| e-ISSN | 10985530 |
| Journal | Journal of Bacteriology |
| Issue Number | 5 |
| Volume Number | 177 |
| Language | English |
| Publisher Date | 1995-03-01 |
| Access Restriction | Open |
| Subject Keyword | Research in Higher Education |
| Content Type | Text |
| Resource Type | Article |
| Subject | Molecular Biology Microbiology |
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