Updated publication reference for PubMed record(s): 30541839. Assay of recombinant Pseudomonas phage PhiKZ gp54 with the prohead protease gp175. The gene for each protein was cloned into the expression plasmid DH10B. The assay was conducted in a lysate of E. coli DH10B cells, conditions in which PhiKZ gp175 had previously been shown to be active. Analyses of gel slices identified C-terminal processing of gp54 via the semi-tryptic peptide 558-FITAMDAAAAAAGVTVTME-576 in the gp54-plus-gp175 slices (predominantly slice 3) provided convincing evidence for proteolysis of gp54 in the presence of gp175.