Structure function correlation of multiple cysteine proteases from a tropical plant Ervatamia coronaria

C and M B Division, Saha Institute of Nuclear Physics, Kolkata-64
â—‹Sampa Biswas Chandana Chakrabarti J.K. Dattagupta Raka Ghosh Sibani Chakraborty

Proteases represent a single class of enzymes which plays an important role in physiological processes and in the commercial field. The papain-like cysteine proteases (family C1A) from plants have been described as catalysts in many physiological processes and are involved in the plant defense mechanism against pathogens and insects. The existence of multiple genes (30 genes in Arabidopsis genome) for this family in a single species and their product, executing similar catalytic mechanism, need to be explored. Fortunately this protease family includes members having long history of structural and functional analysis which makes them an ideal subject for structural genomics project of plant. Three such proteases Ervatamin A, B, and C (from the same source) have been isolated and purified from the latex of the tropical plant Ervatamia coronaria, biochemically, biophysically characterised and three-dimensional structures solved by the X-ray diffraction method. They have been cloned for sequence analysis and future protein engineering project on these enzymes. Though their basic catalytic mechanism and overall folding are similar, they differ in overall charges (pI values), stability and substrate specificity. The amino acid sequence comparison and finally three dimensional structures of these proteases explain how nature tailored array of enzymes known to be involved in defense mechanism to cope with the diverse need in environmental stress. This will also address the question of functional redundancy and evolution of catalytic mechanism for closely related members of a multigene family in plants.