Structural, kinetic and thermodynamic characterizations of SDS-induced molten globule state of a highly negatively charged cytochrome c

R Jain, D Sharma, R Kumar… - The journal of …, 2019 - academic.oup.com
The journal of biochemistry, 2019academic.oup.com
This study presents the structural, kinetic and thermodynamic characterizations of previously
unknown submicellar concentrations of SDS-induced molten globule (MGSDS) state of a
highly negatively charged base-denatured ferricytochrome c (UB-state) at pH∼ 12.8 (±0.2).
The far-UV CD, near-UV CD, ANS-fluorescence data of UB-state in the presence of different
concentrations of SDS indicate that the submicellar concentrations of SDS (≤ 0.4 mM)
transform the UB-state to MGSDS-state. The MGSDS-state has native-like α-helical …
Abstract
This study presents the structural, kinetic and thermodynamic characterizations of previously unknown submicellar concentrations of SDS-induced molten globule (MGSDS) state of a highly negatively charged base-denatured ferricytochrome c (UB-state) at pH ∼12.8 (±0.2). The far-UV CD, near-UV CD, ANS-fluorescence data of UB-state in the presence of different concentrations of SDS indicate that the submicellar concentrations of SDS (≤0.4 mM) transform the UB-state to MGSDS-state. The MGSDS-state has native-like α-helical secondary structure but lacks tertiary structure. The free energy change (ΔG°D) for UB→ MGSDS transition determined by far-UV CD (∼2.7 kcal mol−1) is slightly higher than those determined by fluorescence (∼2.0 kcal mol−1) at 25°C. At very low SDS and NaCl concentrations, the MGSDS-state undergoes cold denaturation. As SDS concentration is increased, the thermal denaturation temperature increases and the cold denaturation temperature decrease. Kinetic experiments involving the measurement of the CO-association rate to the base-denatured ferrocytochrome c at pH ≈12.8 (±0.2), 25°C indicate that the submicellar concentrations of SDS restrict the internal dynamics of base-denatured protein.
Oxford University Press
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