Genetic approaches to study export of lamB to the outer membrane

The authors are studying the molecular mechanism of cellular protein localization. The availability of genetic techniques, such as gene fusion in Escherichia coli, has made this subject particularly amenable to study in the prokaryote. They have constructed a variety of strains in which the gene coding for an outer membrane protein is fused to the gene coding for a normally cytoplasmic enzyme, β-galactosidase. The hybrid proteins produced by such strains retain β-galactosidase activity; this activity serves as a simple biochemical tag for studying the localization of the outer membrane protein. In addition, they have exploited phenotypes exhibited by certain fusion strains to isolate mutants that are altered in the process of protein export. Genetic and biochemical analyses of such mutants have provided important insights into the mechanism of protein localization.