OAR, A 115-KILODALTON MEMBRANE-PROTEIN REQUIRED FOR DEVELOPMENT OF MYXOCOCCUS-XANTHUS

Myxococcus xanthus is a developmental gram-negative bacterium which fo rms multicellular fruiting bodies upon nutrient starvation. This bacte rium was found to contain a 115-kDa membrane protein which separated w ith the inner membrane fraction by sucrose density gradient centrifuga tion. The gene for this protein was cloned, and its DNA sequence was d etermined. The deduced amino acid sequence consists of 1,061 residues. This protein contains a putative signal sequence and many short segme nts, 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 sec ond open reading frame was found 36 bases downstream of the oar termin ation codon. This open reading frame encodes a protein of 236 residues and contains a putative lipoprotein signal sequence. An oar disruptio n mutation (DELTAoar) showed no effect on vegetative growth but caused abnormal morphogenesis during development and reduced myxospore forma tion. When examined with a light microscope, DELTAoar cells were unabl e to aggregate on developmental agar, indicating that Oar is required for cellular adhesiveness during development.