Sequence of amino acids in lamB responsible for spontaneous ejection of bacteriophage lambda DNA

The DNA sequence of the promoter-distal half of lamB from Shigella sonnei 3070 has been determined and compared with the known sequence for the Escherichia coli K12 gene. The only predicted amino acid changes in this region of LamB, the receptor protein for bacteriophage lambda, lie between positions 381 and 390, where seven of the ten amino acids are altered. Evidence is presented that indicates that this region is responsible for the ability of the S. sonnei receptor, but not the E. coli receptor, to trigger spontaneous ejection of DNA from the bacteriophage in vitro. DNA injection in vivo must be more complex and involve also the host Pel protein and the lambda tail proteins gpJ, gpH, and gpV.