AmbB is a putative nonribosomal peptide synthase from Pseudomonas aeruginosa, which is involved in the production of IQS, a potent cell-cell communication signal molecule that integrates the quorum-sensing mechanism and stress response. It consists of 1249 amino acids and contains an AMP-binding domain, a phosphopantetheine-binding (PB) domain and a condensation (C) domain. In this report, a truncated form of AmbB that contains the PB domain and the condensation domain was overexpressed with an N-terminal GST tag in Escherichia coli and purified as a monomer using affinity and size-exclusion chromatography. The recombinant AmbBc (comprising residues 727-1249 of full-length AmbB) was crystallized using the hanging-drop vapour-diffusion method and a full data set was collected to 2.45 Å resolution using a synchrotron-radiation source. The crystals belonged to space group P6122 or P6522, with unit-cell parameters a = b = 87.81, c = 286.8 Å, [alpha] = 90, [beta] = 90, [gamma] = 120°, and contained one molecule per asymmetric unit.