Figure 4.

Formation of PII/GlnK heterotrimers in vitro by denaturation-renaturation procedure. Samples of pure PII or GlnK or mixtures of the two were either untreated or treated with a denaturation-renaturation procedure (see Materials and Methods). Samples corresponding to 2 μg of protein were applied to each lane and were separated on a 8% native gel followed by staining Coomassie brilliant blue to visualize the protein bands. Lanes: 1, untreated PII; 2, untreated GlnK; 3, treated PII; 4, treated GlnK; 5–7, PII/GlnK mixtures in 1:1, 1:2, and 2:1 ratios, respectively, that were treated. Lane 8 shows a similar 8% native gel of untreated 1:2 mixture of PII:GlnK separating as homotrimers compared with a treated sample (lane 9), indicating that heterotrimers are not formed in the stacking gel.