Conformational changes in deoxyribonuclease I in anionic and cationic surfactant solutions

Area of Science:

• Biochemistry
• Protein Chemistry
• Enzymology

Background:

• Bovine pancreatic deoxyribonuclease I (DNAse I) is a crucial enzyme involved in DNA degradation.
• Surfactants are known to interact with and alter protein structures.
• Understanding surfactant-protein interactions is vital for biochemical and pharmaceutical applications.

Purpose of the Study:

• To investigate the effects of sodium dodecylsulfate (SDS) and dodecyltrimethylammonium chloride (DTAC) on the conformation and enzymatic activity of DNAse I.
• To elucidate the role of Ca2+ ions in modulating the interaction between DNAse I and SDS.

Main Methods:

• Fluorescence spectroscopy was employed to monitor changes in protein conformation.
• Circular dichroism (CD) spectroscopy was used to assess alterations in secondary structure.
• Enzymatic activity assays were performed to determine the functional impact of surfactant treatment.

Main Results:

• SDS (1 mM) induced a partial conformational transition in DNAse I, evidenced by a 60% fluorescence quenching and a decrease in ellipticity at 222 nm, indicating secondary structure degradation.
• The conformational changes induced by SDS were partially mitigated by the presence of Ca2+ ions.
• DTAC did not induce any significant changes in DNAse I conformation or enzymatic activity.
• SDS abolished the enzymatic activity of DNAse I, correlating with observed conformational changes.

Conclusions:

• SDS significantly destabilizes the structure of DNAse I, leading to loss of enzymatic function.
• DTAC does not exhibit similar disruptive effects on DNAse I.
• The findings highlight the differential impact of anionic (SDS) and cationic (DTAC) surfactants on enzyme structure and activity, with implications for protein stability studies.