Catalyzes the synthesis of citryl-L-2,3-diaminopropionic acid from L-2,3-diaminopropionic acid (L-Dap) and citrate, the first step in staphyloferrin B biosynthesis. (S)-2,3-diaminopropanoate + ATP + citrate = 2-[(L-alanin-3-ylcarbamoyl)methyl]-2-hydroxybutanedioate + AMP + diphosphate kcat is 16.08 min(-1) with citrate as substrate. Siderophore biosynthesis. Forms a mixture of monomer and dimer in solution. Up-regulated under iron-deficient growth conditions. Repressed by Fur under iron-rich growth conditions. Mutant shows a growth defect in iron-deficient medium and is significantly attenuated in a murine kidney abscess model of infection. Belongs to the IucA/IucC family.