Structural highlights
Function
[AGGL_ABRPR] The A chain is responsible for inhibiting protein synthesis through the catalytic inactivation of 60S ribosomal subunits by removing adenine from position 4,324 of 28S rRNA (By similarity). Less toxic than abrin-a.[1] [UniProtKB:P28590] The B chain is a galactose-specific lectin that facilitates the binding to the cell membrane that precedes endocytosis (By similarity).[2] [UniProtKB:P28590]
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
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.
Structure-function analysis and insights into the reduced toxicity of Abrus precatorius agglutinin I in relation to abrin.,Bagaria A, Surendranath K, Ramagopal UA, Ramakumar S, Karande AA J Biol Chem. 2006 Nov 10;281(45):34465-74. Epub 2006 Jun 13. PMID:16772301[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Liu CL, Tsai CC, Lin SC, Wang LI, Hsu CI, Hwang MJ, Lin JY. Primary structure and function analysis of the Abrus precatorius agglutinin A chain by site-directed mutagenesis. Pro(199) Of amphiphilic alpha-helix H impairs protein synthesis inhibitory activity. J Biol Chem. 2000 Jan 21;275(3):1897-901. PMID:10636890
- ↑ Liu CL, Tsai CC, Lin SC, Wang LI, Hsu CI, Hwang MJ, Lin JY. Primary structure and function analysis of the Abrus precatorius agglutinin A chain by site-directed mutagenesis. Pro(199) Of amphiphilic alpha-helix H impairs protein synthesis inhibitory activity. J Biol Chem. 2000 Jan 21;275(3):1897-901. PMID:10636890
- ↑ Bagaria A, Surendranath K, Ramagopal UA, Ramakumar S, Karande AA. Structure-function analysis and insights into the reduced toxicity of Abrus precatorius agglutinin I in relation to abrin. J Biol Chem. 2006 Nov 10;281(45):34465-74. Epub 2006 Jun 13. PMID:16772301 doi:http://dx.doi.org/10.1074/jbc.M601777200
