Figure 6. A minimal polybasic stretch at the C-terminus of the [p67^phox – Rac1] chimeras is essential for the support of NADPH oxidase activity. Four mutants of the prototype chimera 3 were constructed in which 1, 3, 4, or 6 basic residues were replaced by glutamines. The numbering of chimeras are according to Alloul et al.⁷⁹ (A) NADPH oxidase supporting activity of the mutant chimeras, in nonprenylated form, was assessed in an amphiphile-dependent cell-free assay consisting of phagocyte membrane, chimera in the GTPγS-bound form, and p47^phox. (B) The activity of the equivalent prenylated chimeras was measured in an amphiphile-independent cell-free system, consisting of membrane and chimera in the GTPγS-bound form, in the absence of p47^phox (modified from ref. 83).