FIGURE 6.

Intra-cavity folding of Rubisco with and without the GroEL C termini monitored by intramolecular FRET. Rubisco folding inside full-length and truncated single ring GroEL-GroES complexes monitored by intramolecular FRET with four different site pairs as follows: a, 356ED-58F; b, 209ED-58F; c, 34ED-454F, and d, 454ED-58F. Chemically denatured, fluorescently labeled Rubisco (100 nm) was bound to full-length SR1 or SRΔ526 (500 nm). This complex was rapidly mixed with an equal volume of excess GroES (1 μm) and ATP (2 mm) in a stopped-flow apparatus. Shown is the average of n = 12 replicates of matched experimental pairs, calculated from donor-only and donor-acceptor samples. Sampling time was 150 ms. In all cases, the change in FRET efficiency was well fit by a bi-exponential rate law (black line), and the average folding rate constant is shown for each case. Table 2 contains the rate constants for each fit.