Membrane Proteome


The TopicPages involved with the Localization of EcoProteins to Membranes are subdivided into Inner Membrane Proteins (IMemProt), Outer Membrane Proteins (OMemProt), and Lipoproteins (LipoProt), each with their own TopicPages. The IMemProt and OMemProt designations are based on experimental 2DMS protein identifications that include lipoproteins, which are localized to either the OM or IM. IMemProt and OMemProt include predictions for non-lipoprotein inner or outer membrane proteins. Experimentally verified lipoproteins (LipoProt_Veri) are distinguished from probable lipoprotein predictions supported by homology analysis (LipoProt_Prob), and predictions of likely lipoproteins without homology support (LipoProt_Pred), as described on the LipoProteome subTopicPage.


In addition to serving as a SuperTopic Index for Membrane Protein TopicPages, this Membrane Proteome TopicPage serves as a guide to the biology of E. coli K-12 membrane proteins in general. As an initial focus, recent localizations based on 2DMS (two dimensional gel electrophoresis of subfractions followed by spot identification using mass spectrometry methods) are grouped as subTopics of the Membrane Proteome Topic. If inner and outer membrane fractionation was not performed, they are added to the Mem_Loc_2DMS subTopic. Other 2DMS studies may have further localized the membrane proteins and they are summarized on the other Membrane Protein TopicPages.

A recent study by Lai (2004) identified 28 E. coli proteins from rod and minicell membrane preparations. They did not separate inner and outer membranes. These 28 proteins are grouped into the subTopic Mem_Loc_2DMS for
"Experimentally determined membrane protein localization based on pre-fractionation, two dimensional polyacrylamide gel electrophoresis and identification by Mass Spectroscopy".
These proteins can usually be localized to either the inner or the outer membrane fractions, and these assignments, based on 2DMS data in other publications, or other types of localization experiments, or bioinformatics predictions, are noted in the GenePages, so they may be included in other Proteomics subTopics based or other referenced post-genomic studies.

Lai EM, Nair U, Phadke ND, Maddock JR, Proteomic screening and identification of differentially distributed membrane proteins in Escherichia coli, Mol Microbiol (2004) 52:1029-44.9

Lai (2004) used minicell/rod-enrichment as a screen for asymmetrically localized membrane proteins, and further showed polar OmpW and polar/septal YiaF. Lai (2004) washed with alkaline carbonate to reduce cytoplasmic protein contamination. This may also have removed some membrane-associated proteins.