Abstract:

The secondary structure of cold-adapted protease MCP-01 and mesophilic protease BP-01 were investigated by circular dichroism (CD). According to the result of CD spectra, there are lower content of α-helixes and higher content of random in MCP01 than in BP-01, which led to its higher flexibility and lower stability in structure. The temperature leading to loss of 50% secondary structure of protease MCP-01 was lower 10.7℃ than BP-01. The effects of denaturant guanidine hydrochloride (GuHCl) and 2,2,2Trifluoroethanol (TFE) on cold-adapted protease MCP-01 and mesophilic protease BP-01 were studied. The results of CD spectra indicated that the unfolding concentration of GuHCl for MCP-01 and BP-01 were 1.0 M and 3.0 M， respectively. Moreover, the CD spectra showed that the structure of MCP-01 and BP-01 had no obvious changes when TFE concentrations were lower 20% and 30%, respectively. When TFE concentration was further increased， the structure of MCP-01 and BP-01 began to denature. These results indicated that the stability of MCP-01 was less than that of BP-01 and it was denatured at lower GuHCl or TFE concentration. The conformation changes of protease MCP-01 and BP-01 were studied during incubation. The stability of MCP-01 was affected  significantly by different buffer system and increased successively in the following order: carbonate

Key words: conformation, circular dichroism, cold-adapted protease, mesophilic protease