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Oar, a 115-kilodalton membrane protein required for development of Myxococcus xanthus
M Martinez-Canamero1, J Munoz-Dorado, E Farez-Vidal
1Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway 08854.
Abstract:
Myxococcus xanthus is a developmental gram-negative bacterium which forms multicellular fruiting bodies upon nutrient starvation. This bacterium was found to contain a 115-kDa membrane protein which separated with the inner membrane fraction by sucrose density gradient centrifugation. The gene for this protein was cloned, and its DNA sequence was determined. The deduced amino acid sequence consists of 1,061 residues. This protein contains a putative signal sequence and many short segments, found scattered throughout the entire protein, that have sequence similarities with OmpA, a major outer membrane protein of Escherichia coli. Thus, the gene was designated oar (OmpA-related protein). A second open reading frame was found 36 bases downstream of the oar termination codon. This open reading frame encodes a protein of 236 residues and contains a putative lipoprotein signal sequence. An aor disruption mutation (delta oar) showed no effect on vegetative growth but caused abnormal morphogenesis during development and reduced myxospore formation. When examined with a light microscope, delta oar cells were unable to aggregate on developmental agar, indicating that Oar is required for cellular adhesiveness during development.
Insights
Myxococcus xanthus OmpA-related protein (Oar) is crucial for multicellular development. A mutation in the Oar gene disrupts fruiting body formation and reduces spore production, highlighting its role in cell adhesion.
Area of Science:
- Microbiology
- Molecular Biology
- Developmental Biology
Background:
- Myxococcus xanthus is a gram-negative bacterium known for forming multicellular fruiting bodies during nutrient starvation.
- Membrane proteins play vital roles in bacterial cell structure and function, particularly during developmental processes.
Purpose of the Study:
- To identify and characterize a novel membrane protein in Myxococcus xanthus involved in its developmental cycle.
- To elucidate the function of the OmpA-related protein (Oar) in bacterial morphogenesis and cell adhesion.
Main Methods:
- Sucrose density gradient centrifugation was used to isolate membrane protein fractions.
- Gene cloning and DNA sequencing were performed to determine the genetic basis of the protein.
- Gene disruption (mutagenesis) was employed to study the protein's function in vivo.
Main Results:
- A 115-kDa membrane protein, designated Oar, was identified and its gene sequenced.
- The Oar gene encodes a protein with similarities to Escherichia coli OmpA, containing a putative signal sequence.
- Disruption of the oar gene impaired multicellular development, specifically cellular aggregation and myxospore formation, without affecting vegetative growth.
Conclusions:
- Oar is essential for Myxococcus xanthus cellular adhesiveness during multicellular development.
- The OmpA-related protein plays a critical role in the complex developmental pathway of this bacterium.
- Further research into Oar may reveal new insights into bacterial adhesion mechanisms and developmental regulation.