CcdB at pH 4 forms a partially unfolded state with a dry core

pH is an important factor that affects the protein structure, stability and activity. Here we probe the nature of the low pH structural form of the homodimeric CcdB protein (Controller of Cell Death B). Characterization of CcdB protein at pH 4 and 300K using circular dichroism spectroscopy, ANS binding and Trp solvation studies suggests that it forms a partially unfolded state with a dry core at equilibrium under these conditions. CcdB remains dimeric at pH 4 as shown by multiple techniques, such as SEC-MALS, analytical ultra-centrifugation and electron paramagnetic resonance.

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