Abstract: A process for cleavage of a protein (a) sequence from a protein containing the tetrapeptide sequence Pro-Xyz-Gly-Pro, wherein Xyz can be any desired amino acid, and reacting the protein with a collagenase whereby the Xyz-Gly bond is selectively cleaved, thereby producing a protein with the sequence Gly-Pro at its N-terminal end; or (b) containing the sequence Met-Pro; and subsequently selectively cleaving the glycine or methionine residue from the N-terminal end of the product protein with an aminoacylproline aminopeptidase and selectively cleaving the proline residue therefrom with a proline aminopeptidase; or subsequently selectively cleaving the Gly-Pro or Met-Pro residue from the N-terminal end of the produced protein using a postproline dipeptidylaminopeptidase.

Abstract: PhoA mutant E. coli SB44, prepared by mutation of E. coli HB101 with an N-nitroso compound, can be used to identify and isolate recombinant plasmids into which a phoA gene has been incorporated. These plasmids can be used to transform bacteria which can be cloned and incubated to provide alkaline phosphatase in high yield. Moreover, these plasmid vectors can be modified in various ways so that the N-terminal amino acid sequence of phoA is followed in reading phase by the DNA coding for some other protein. In turn, these new plasmids can be used to transform bacteria which can be cloned and incubated to produce fusion proteins comprising the desired other protein in high yield and outside of the cell membrane in the periplasmatic space.