Figure 4.

Phr peptide sequence-dependent specificity for target recognition. (A) Amino acid sequence of PhrA and PhrC pentapeptides and their modified forms obtained by single amino acid replacement at position 1, 3, and 4 of PhrApep5 with the corresponding residue of PhrCpep5 and vice versa. The ability of the mutant peptides to inhibit RapA (B) or RapB (C) phosphatase activity (5 μM) on Spo0F∼P (10 μM) was tested in the standard reaction conditions described in Materials and Methods. Peptides were all used at 200 μM final concentration. The control level of Spo0F phosphorylation is shown in lane 1 whereas the dephosphorylation of Spo0F∼P by RapA or RapB is in lane 2. Lanes 3–10 contain the peptides in the order indicated by the numbers in parentheses.