Abstract
OmpF and OmpC are major outer membrane proteins. Although they are homologous proteins, they function differently in several respects. As an approach to elucidate the submolecular structures that determine the difference, a method was developed to construct a series of ompF-ompC chimeric genes by in vivo homologous recombination between these two genes, which are adjacent on a plasmid. The genomic structures of these chimeric genes were determined by restriction endonuclease analysis and nucleotide sequence determination. In almost all cases, recombination took place between the corresponding homologous regions of the ompF and ompC genes. Many of the chimeric genes produced proteins that migrated to various positions between the OmpF and OmpC proteins on polyacrylamide gel. On the basis of the results, a domain contributing to the mobility difference the OmpF and OmpC proteins was identified. Some chimeric genes did not accumulate outer membrane proteins, despite the fact that the fusion of the ompF and ompC genes was in frame. Bacterial cells possessing the chimeric proteins were also tested as to their sensitivity to phages which require either OmpF or OmpC as a receptor component. The chimeric proteins were either of the OmpF or OmpC type with respect to receptor activity. Based on the observations, the roles of submolecular domains in the structure, function, and biogenesis of the OmpF and OmpC proteins are discussed.