Systematic Identification Of Sub-proteome Of Escherichia Coli Cell Envelope Reveals The Interaction Network Of Membrane Proteins And Membrane-associated Peripheral Proteins

Membrane proteins of Gram-negative bacteria are key molecules that interface the cells with the environment. For this case, study of outer membrane componets and complexes is very interesting to theory and practice application.Despite recent proteomic identification of a lot of oligomer proteins in E. coli cell envelope, the protein complex of E. coli membrane proteins and their peripherally associated proteins remains ill defined. In the current study, we systematically analyze the sub-proteome of E. coli cell envelope enriched in sarcosine-soluble fraction (SSF) by using proteomic methodologies. 76 proteins out of 117 spots on 2-DE electrophoresis gels are identified, and combining the 2-DE map of sarcosine-insoluble fraction (SIF) of E. coli cell envelope, 31 outer membrane proteins (OMPs) are identified totally.Importantly, our further proteomic studies reveal a number of previously unrecognized membrane-interacting protein complexes, such as the complex consisting of OmpW and fumarate reductase. This established complete proteomic profile of E. coli envelope also sheds new insight into the function(s) of E. coli outer envelope.For an further understanding of the OmpW complex, we established native/SDS-PAGE separation maps of membrane protein complex with the peripheral associated proteins of K-12 cultured in LB medium of different concentration of the ferrous iron chelator DIP and dope FeCl3 after being cultured 3h, and in LB medium with different antibiotics. The results indicate that the OmpW complex kept intact or isolated, respectively, in antibiotic environment and by > 150μm DIP.