A gram-negative bacterial cell is described that is deficient in a chromosomal
gene present in a wild-type such cell which gene shares at least 80% sequence identity
with the native sequence of the yfcK gene and encodes an aminopeptidase. Alternatively,
a gram-negative bacterial cell is deficient in a chromosomal gene present in a
wild-type such cell which gene encodes an aminopeptidase that shares at least 80%
sequence identity with the native sequence of aminopeptidase b2324. Either of these
types of cells, when comprising a nucleic acid encoding a heterologous polypeptide,
produces an N-terminal unclipped polypeptide when it is cultured and the polypeptide
recovered, with virtually no N-terminal clipped polypeptide produced as an impurity.
Conversely, a method is provided for cleaving an N-terminal amino acid from a polypeptide
comprising contacting the polypeptide with an aminopeptidase sharing at least 80%
sequence identity with the native sequence of aminopeptidase b2324.
