The Escherichia coli K12 lambda receptor is a multifunctional outer membrane protein whose precursor, encoded in gene lamB, is cleaved during export. We present the DNA sequence of lamB and of the distal region that contains repetitive and palindromic sequences and could give rise to highly stable mRNA structures. The calculated molecular weight of the lambda receptor is 47,400. Of the 421 amino acids, 89 are charged, mostly negatively. No region devoid of charged amino acids and long enough to serve as a transmembrane portion is detected. The distribution of charges presents special features that we comment upon in relation to the structure, functions and localization of the lambda receptor. Gene lamB is followed by molA, an unidentified reading frame corresponding to a 131-amino-acid peptide with the characteristics of an exported protein.