FIGURE 9.

A, Working model for cpSRP43-mediated disaggregation reaction. Step 1 depicts initial binding of cpSRP43 (magenta) to the LHCP aggregate (green), which occurs via recognition of the solvent-exposed L18 motif (red). Step 2 depicts the cooperative action of cpSRP43 molecules to compete with and disrupt the packing interactions between the LHCP TM segments within the aggregate, leading to its resolubilization. B and C, qualitative free energy diagrams summarizing the effects of the L18-binding mutants that disrupt the initial binding step (B) and the irreversible TM mutants that disrupt the remodeling step (C), as described under “Results.” The figures are not drawn to scale.