Analysis of Intracellular Proteins of E. coli Inactivated by High Pressure Carbon Dioxide
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Abstract:
The variation of proteins in E. coli after 10~50 MPa HPCD treatment at 37 ℃ for 30 min was investigated in this study. The total bacterial counts, cell structure, protein solubility, proteome and secondary structure of protein were analyzed. The results showed that the logarithm of the total bacterial counts of E. coli after HPCD treatment was significantly decreased when the pressure increased to 30 MPa. The cell structure did not change with different HPCD treatments (10~50 MPa). The soluble protein content significantly decreased from 1.77 mg/mL to 0.57 mg/mL when the extraction of E. coli proteins was treated by 20 MPa HPCD in comparison with control (0.1 MPa treatment). The content of proteins decreased as the pressure of HPCD increased. Forty-six protein spots with the greatest expression difference were isolated from the control group and 30 MPa HPCD treatment group using two-dimensional gel electrophoresis. There were 16 representative protein spots were identified by MALDI TOF/TOF mass spectrometry, which were involved in cytoskeleton structure, cell metabolism, transmission of signal and transcription. The circular dichroism results of protein solutions showed that the α-helix accounted for 68.04% and the β-sheet accounted for 0.33% in the control group. The α-helix content significantly decreased (P<0.05) as the pressure of HPCD increased, while theβ-sheet content significantly increased (P<0.05) when treated by 20 MPa HPCD, but no further change occurred when the pressure continued to increase.
