1o0e
From Proteopedia
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1.9 Angstrom Crystal Structure of a plant cysteine protease Ervatamin C
Overview
Ervatamin C is an unusually stable cysteine protease from the medicinal, plant Ervatamia coronaria belonging to the papain family. Though it, cleaves denatured natural proteins with high specific activity, its, activity toward some small synthetic substrates is found to be, insignificant. The three-dimensional structure and amino acid sequence of, the protein have been determined from X-ray diffraction data at 1.9 A (R =, 17.7% and R(free) = 19.0%). The overall structure of ervatamin C is, similar to those of other homologous cysteine proteases of the family, folding into two distinct left and right domains separated by an active, site cleft. However, substitution of a few amino acid residues, which are, conserved in the other members of the family, has been observed in both, the domains and also at the region of the interdomain cleft. Consequently, the number of intra- and interdomain hydrogen-bonding interactions is, enhanced in the structure of ervatamin C. Moreover, a unique disulfide, bond has been identified in the right domain of the structure, in addition, to the three conserved disulfide bridges present in the papain family. All, these factors contribute to an increase in the stability of ervatamin C., In this enzyme, the nature of the S2 subsite, which is the primary, determinant of specificity of these proteases, is similar to that of, papain, but at the S3 subsite, Ala67 replaces an aromatic residue, and has, the effect of eliminating sufficient hydrophobic interactions required for, S3-P3 stabilization. This provides the possible explanation for the lower, activity of ervatamin C toward the small substrate/inhibitor. This, substitution, however, does not affect the binding of denatured natural, protein substrates to the enzyme significantly, as there exist a number of, additional interactions at the enzyme-substrate interface outside the, active site cleft.
About this Structure
1O0E is a Single protein structure of sequence from Tabernaemontana divaricata with THJ as ligand. Full crystallographic information is available from OCA.
Reference
Structural basis of the unusual stability and substrate specificity of ervatamin C, a plant cysteine protease from Ervatamia coronaria., Thakurta PG, Biswas S, Chakrabarti C, Sundd M, Jagannadham MV, Dattagupta JK, Biochemistry. 2004 Feb 17;43(6):1532-40. PMID:14769029
Page seeded by OCA on Tue Nov 20 22:42:21 2007
