The dynamics of assembly of a cytoplasmic membrane protein in Escherichia coli.

ABSTRACT The Escherichia coli cell division protein FtsQ is a central component of the divisome. FtsQ is a bitopic membrane protein with a large C-terminal periplasmic domain. In this work we investigated the role of the transmembrane segment (TMS) that anchors FtsQ in the cytoplasmic membrane. A set of TMS mutants was made and analyzed for the ability to complement an ftsQ mutant. Study of the various steps involved in FtsQ biogenesis revealed that one mutant (L29/32R;V38P) failed to functionally insert into the membrane, whereas another mutant (L29/32R) was correctly assembled and interacted with FtsB and FtsL but failed to localize efficiently to the cell division site. Our results indicate that the FtsQ TMS plays a role in FtsQ localization to the division site.

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FtsL, an Essential Cytoplasmic Membrane Protein Involved in Cell Division in Escherichia coli

Journal of Bacteriology ◽

10.1128/jb.174.23.7717.1992 ◽

1992 ◽

Vol 174 (23) ◽

pp. 7717-7728 ◽

Cited By ~ 60

Author(s):

Luz-Maria Guzman ◽

James J. Barondess ◽

Jon Beckwith

Keyword(s):

Escherichia Coli ◽

Cell Division ◽

Membrane Protein ◽

Cytoplasmic Membrane ◽

Topological Analysis ◽

Growth Conditions ◽

Bacterial Cell Division ◽

Leucine Zippers ◽

Protein Dimerization ◽

Membrane Spanning

We have identified a gene involved in bacterial cell division, located immediately upstream of the ftsI gene in the min 2 region of the Escherichia coli chromosome. This gene, which we named ftsL , was detected through characterization of Tn phoA insertions in a plasmid containing this chromosomal region. Tn phoA topological analysis and fractionation of alkaline phosphatase fusion proteins indicated that the ftsL gene product is a 13.6-kDa cytoplasmic membrane protein with a cytoplasmic amino terminus, a single membrane-spanning segment, and a periplasmic carboxy terminus. The ftsL gene is essential for cell growth and division. A null mutation in ftsL resulted in inhibition of cell division, formation of long, nonseptate filaments, ultimate cessation of growth, and lysis. Under certain growth conditions, depletion of FtsL or expression of the largest ftsL-phoA fusion produced a variety of cell morphologies, including Y-shaped bacteria, indicating a possible general weakening of the cell wall. The FtsL protein is estimated to be present at about 20 to 40 copies per cell. The periplasmic domain of the protein displays a sequence with features characteristic of leucine zippers, which are involved in protein dimerization.

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Glycolipozyme membrane protein integrase (MPIase): recent data

BioMolecular Concepts ◽

10.1515/bmc-2014-0030 ◽

2014 ◽

Vol 5 (5) ◽

pp. 429-438 ◽

Cited By ~ 10

Author(s):

Ken-ichi Nishiyama ◽

Keiko Shimamoto

Keyword(s):

Escherichia Coli ◽

Membrane Proteins ◽

Membrane Protein ◽

Structure Determination ◽

Molecular Chaperone ◽

Molecular Mechanisms ◽

Cytoplasmic Membrane ◽

Amino Sugars ◽

Glycan Chain ◽

Preprotein Translocation

AbstractA novel factor for membrane protein integration, from the cytoplasmic membrane of Escherichia coli, named MPIase (membrane protein integrase), has recently been identified and characterized. MPIase was revealed to be essential for the membrane integration of a subset of membrane proteins, despite that such integration reactions have been, thus far, thought to occur spontaneously. The structure determination study revealed that MPIase is a novel glycolipid comprising a glycan chain with three N-acetylated amino sugars connected to diacylglycerol through a pyrophosphate linker. As MPIase catalyzes membrane protein integration, we propose that MPIase is a glycolipozyme on the basis of its enzyme-like function. The glycan chain exhibits a molecular chaperone-like function by directly interacting with substrate membrane proteins. Moreover, MPIase also affects the dimer structure of SecYEG, a translocon, thereby significantly stimulating preprotein translocation. The molecular mechanisms of MPIase functions will be outlined.

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