Bagaria, A., Surendranath, K., Ramagopal, U.A., Ramakumar, S. and Karande, A.A. 2006. Structure-function analysis and insights into the reduced toxicity of Abrus precatorius agglutinin I in relation to abrin. Journal of Biological Chemistry . 281, pp. 34465-34474. https://doi.org/10.1074/jbc.M601777200
| Title | Structure-function analysis and insights into the reduced toxicity of Abrus precatorius agglutinin I in relation to abrin |
|---|---|
| Authors | Bagaria, A., Surendranath, K., Ramagopal, U.A., Ramakumar, S. and Karande, A.A. |
| Abstract | Abrin and agglutinin-I from the seeds of Abrus precatorius are type II ribosome-inactivating proteins that inhibit protein synthesis in eukaryotic cells. The two toxins share a high degree of sequence similarity; however, agglutinin-I is weaker in its activity. We compared the kinetics of protein synthesis inhibition by abrin and agglutinin-I in two different cell lines and found that approximately 200-2000-fold higher concentration of agglutinin-I is needed for the same degree of inhibition. Like abrin, agglutinin-I also induced apoptosis in the cells by triggering the intrinsic mitochondrial pathway, although at higher concentrations as compared with abrin. The reason for the decreased toxicity of agglutinin-I became apparent on the analysis of the crystal structure of agglutinin-I obtained by us in comparison with that of the reported structure of abrin. The overall protein folding of agglutinin-I is similar to that of abrin-a with a single disulfide bond holding the toxic A subunit and the lectin-like B-subunit together, constituting a heterodimer. However, there are significant differences in the secondary structural elements, mostly in the A chain. The substitution of Asn-200 in abrin-a with Pro-199 in agglutinin-I seems to be a major cause for the decreased toxicity of agglutinin-I. This perhaps is not a consequence of any kink formation by a proline residue in the helical segment, as reported by others earlier, but due to fewer interactions that proline can possibly have with the bound substrate. |
| Keywords | Abrin Abrus agglutinin structure function |
| Journal | Journal of Biological Chemistry |
| Journal citation | 281, pp. 34465-34474 |
| ISSN | 0021-9258 |
| Year | 2006 |
| Publisher | American Society for Microbiology and Molecular Biology |
| Digital Object Identifier (DOI) | https://doi.org/10.1074/jbc.M601777200 |
| Publication dates | |
| Published | 2006 |
| Funder | The Indian Council of Medical Research (ICMR) |