Screening for lamB missense mutations which alter all lambda receptor activities in Escherichia coli K12

Previously described missense mutations in gene lamB, the structural gene for the lambda receptor in Escherichia coli K12, affected only some of the activities of this multifunctional protein. We isolated lamB mutations, some of which could be of the missense type, and which affected all of the activities of the LamB protein. Among 8 of these mutations, 5 affected the stability of the LamB protein and 3 did not markedly decrease the amount of LamB protein in the mutant strains. In these 3 cases, the mutated LamB proteins were recovered with the envelope of the mutants. We briefly discuss the nature of these mutations and their possible effects on LamB protein structure and location.