Proteomic Analysis On Outer Membrane Proteins Of Escherichia Coli K-12 In Carbohydrate Metabolism

Escherichia coli, which is a parasite in human or mammal intestines, is also a gram-negative aerobe or facultative anaerobe. Since it is characteristic of wide distribution, good self-reproduction, quick development and simple structure, it has become an important biological mode material in modern life sciences research, especially in molecular genetics and biological engineering fields. This paper investigated the outer membrane proteins (OMPs) of E. coli K-12 by proteomic approach, especially functional proteomics. On the basis of the establishment of E. coli K-12 2-DE map, we studied the OMPs expression difference among bacteria cultured in different glucose concentrations.First, we extracted the E. coli K-12 OMPs by sodium lauroyl sarcosine and identified 16 proteins including 12 OMPs with the combination of 2-DE and PMF methods. This molecular exprerssional profile of E. coli K-12 OMPs provided useful data for further studies.Then, we tested 10 differential OMPs in 2-DE using Western blot. As a result, we found protein expression of Fhue, TolC, OmpA, OmpW, Dps, FadL and OmpC was respectively increased step by step, but that of Ef-Tu, OmpF and OmpT decreased gradually, according to the fact that glucose gradient improved from low to high. These Western blot images confirmed the 2-DE profiles mentioned above and showed that the 10 differential proteins, including 9 OMPs, played an important role during carbohydrate metabolism of Escherichia coli K-12.At last, we analyzed carbohydrate metabolism difference among gene knockout strain, rescue strain and wild type strain of Escherichia coli K-12 using functional genomics technologies. The work led us to the conclusion that OmpA helped to improve the outer membrane permeability of glucose, while TolC, OmpW, OmpC, OmpF, Dps, FadL and OmpT decreased the permeability and repulsed glucose. Furthermore, carbohydrate metabolism of Escherichia coli K-12 was regulated by EnvZ/OmpR, a double-component signal transduction system. All the experiments conducted and their results proved that outer membrane proteins of Gram negative bacteria played a functionally important role during carbohydrate metabolism.