Molecular basis of the am8H1 lesion in bacteriophage M13.

The nucleotide sequence of the mutant region of am8H1, the only conditional lethal mutant in gene VIII of the filamentous phages, has been determined and compared to the wild-type sequence. The amber mutation lies adjacent to the codons specifying the cleavage site for the procaryotic signal peptidase (1). The precoat protein of this mutant appears to be processed normally in the amber-suppressing strain K37, which inserts a serine residue in place of a glutamic acid residue present in the wild-type precoat protein. The amino acid compositions of wild-type and mutant phage are in agreement with the sequence data.