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Molecular characterization of an Enterobacter cloacae outer membrane protein (OmpX)
J Stoorvogel1, M J van Bussel, J Tommassen
1Department of Medical Microbiology, University Hospital, Leiden, The Netherlands.
Journal of Bacteriology
|January 1, 1991
Summary
Researchers cloned the Enterobacter cloacae outer membrane protein X (OmpX) gene. OmpX overproduction reduced porin levels in bacterial outer membranes, suggesting a role in membrane protein regulation.
Area of Science:
- Microbiology
- Molecular Biology
- Structural Biology
Background:
- Outer membrane proteins (OMPs) are crucial for Gram-negative bacteria.
- Enterobacter cloacae possesses a unique OmpX outer membrane protein.
- Understanding OmpX function and structure is key to bacterial physiology.
Purpose of the Study:
- To clone and characterize the Enterobacter cloacae ompX gene.
- To investigate the effect of OmpX overproduction on outer membrane composition.
- To determine the nucleotide sequence and protein structure of OmpX.
Main Methods:
- Gene cloning using gamma delta sequence insertion.
- In vitro transcription and translation for gene polarity.
- M13 dideoxy sequencing for nucleotide sequence determination.
- N-terminal sequencing of mature OmpX protein.
Main Results:
- The ompX gene was successfully cloned and sequenced.
- OmpX precursor protein has 172 amino acids (18.6 kDa) with a 23-amino acid signal sequence.
- OmpX overproduction decreased porin quantities in Enterobacter cloacae and E. coli.
- OmpX is hydrophilic with short hydrophobic stretches, typical of Gram-negative OMPs.
Conclusions:
- The ompX gene encodes a novel outer membrane protein.
- OmpX influences outer membrane protein composition, potentially regulating porin levels.
- A model for OmpX folding in the outer membrane was proposed.