Characterization, prokaryotic expression and purification of a rice cysteine protease OsCP2.

Cysteine protease is an important hydrolysis protease which participates in seed germination, seedling growth, stress response, tissue differentiation, senescence and so on. OsCP2 (Oryza sativa cysteine protease 2) is a putative cysteine protease gene in rice, and its cDNA is 2 279 bp in length with two extrons and one intron. The open reading frame of OsCP2 is 1 089 bp in length encoding a 362 amino acid peptide, with a signal peptide of 36 amino acids at the N-terminus. Phylogenetics analysis showed that OsCP2 has the highest homology with barley cysteine protease HvCP, and they belong to papain subfamily. In addition, a recombinant vector pET32a/CP2 was constructed, and the recombinant OsCP2 protein was expressed in E.coli strain BL21DE3 with a molecular weight of 58 kD. Furthermore we purified the recombinant OsCP2 protein from the inclusion body with a purity more than 90%. This result is helpful for the further study of OsCP2 function.