Description:
76 proteins have been identified in inner membrane preparations by 2D-gel
fractionation and MS identification of many protein isoform spots:
Lopez-Campistrous (2005)
An additional two Inner Membrane proteins are included in this Topic from another 2DMS study:
Lai (2004)
Details:
The 76 proteins localized to the inner membrane,
as identified in Supplementary Table 3 of Lopez-Campistrous( 2005),
are labeled in EcoGene as IMem_Loc_2DMS.
Unlike the IMemProt, the IMem_Loc_2DMS proteins are not all predicted to have membrane spanning regions
or to be integral membrane proteins.
Many of these IM-localized proteins bind to integral membrane proteins or have single membrane
spanning domains predicted. In fact, only 7/738 IMemProts were identified among the 76 IMem_Loc_2DMS proteins:
cld, msbA, mtlA, pntB, sohB, tsr and yqiK.
The 2D gel step may have enriched for membrane-associated proteins with soluble domains, including some lipoproteins (LipoProt) excluded from the IMemProt classification.
Some proteins with known or suspected cytoplasmic, periplasmic and outer membrane locations were assigned
an inner membrane location in this study. This may result from some proteins sticking to inner membranes
during sample preparation or from cross-contamination of cell fractions.
However, it is likely that most, if not all, of these proteins do associate with the
inner membrane, or inner membrane complexes, in vivo, in physiologiocally relevant interactions.
In another study using 2D_MS to identify membrane proteins, Lai (2004) examined total membrane
preparations from minicells and rods to look for proteins with polar and septal localization.
OmpW was identified as an outer membrane protein localized to the cell
poles and the membrane protein YiaF was identified as having
a polar and septal location bias.
The five inner membrane proteins identified by Lai (2004) include AtpA, YiaF and AcrA,
all also localized to the IM by Lopez-Campistrous (2005), IMemProt_E protein AtpB, and FtsZ,
an inner membrane associated protein bound to the cytoplasmic side that was identified by
Lopez-Campistrous (2005) as a periplasmic protein, perhaps artifactually. ftsZ and atpB are included in the IMem_Loc_2DMS subTopic based on the Lai (2004) results for a total of 78 IMem_Loc_2DMS proteins in EcoGene.
- 2005
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Lopez-Campistrous A, Semchuk P, Burke L, Palmer-Stone T, Brokx SJ, Broderick G, Bottorff D, Bolch S, Weiner JH, Ellison MJ (2005) Localization, annotation, and comparison of the Escherichia coli K-12 proteome under two states of growth. Mol Cell Proteomics 4:1205-9
- 2004
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