Synthesis and maturation of lambda receptor in Escherichia coli K-12: in vivo and in vitro expression of gene lamB under lac promoter control.

Abstract

The .lambda. receptor is an outer membrane protein from E. coli K-12. lamB, its structural gene, is part of the maltose regulon. This gene was cloned in a phage so that it is under the control of the lac promoter. The phage was devised in such a way that it can infect lamB mutants and that chromosomal lamB mutations can be transferred to it. In vivo, the .lambda. receptor is expressed under lac promoter control and is exported normally to the outer membrane, independently of the expression of the other genes of the maltose regulon. In vitro, DNA of the phage allows efficient synthesis of the lamB product. The protein, or pre-.lambda.-receptor, made in vitro contains an NH2-terminal sequence of about 25 amino acids not found in the .lambda. receptor. No inactivation of phage .lambda. by the pre-.lambda.-receptor was detected. Conversion of the pre-.lambda.-receptor to a form that has the apparent MW of the mature .lambda. receptor was achieved. A lamB mutation that blocks export in vivo also blocks conversion in vitro.