Figure 4.

M10^long-GCN4 is dynamic and lacks an all-or-none folding transition. (A) Preparative gel filtration chromatograms from the final stage of purification of M10^short-GCN4, M10^long-GCN4, and M10^long-M5CC. These three proteins elute at 23, 71, and 130 kD, respectively. All three elute at larger masses than predicted from globular standards, as expected for rod-like molecules. However, M10^long-GCN4 elutes at a much greater MW than M10^short-GCN4, even though these two constructs are of similar length. (B) The amide-region ¹H-¹⁵N HSQC spectrum of M10^short-GCN4 illustrates good peak dispersion. (C) The corresponding M10^long-GCN4 HSQC has poor dispersion and has fewer peaks than backbone amides, indicative of conformational dynamics. (D) The M10^short-GCN4 CD melting curve at 222 nm shows a cooperative unfolding transition. (E) The corresponding M10^long-GCN4 CD shows gradual helical fraying without evidence of a cooperative transition. To see this figure in color, go online.