Secondary structure induction in aqueous vs membrane-like environments

Area of Science:

• Biochemistry
• Structural Biology
• Biophysics

Background:

• Understanding amino acid conformational propensities is crucial for predicting protein structure and function.
• Previous studies often lacked investigation in biologically relevant lipidic environments.

Purpose of the Study:

• To determine the intrinsic alpha-helical or beta-sheet propensity of all 20 naturally occurring amino acids.
• To investigate how different environments (aqueous, protein interior-like, membrane-like) affect these propensities.
• To elucidate the role of hydrophobic interactions in conformational induction within lipidic environments.

Main Methods:

• Utilized a polyalanine-based model host peptide (Ac-KYA13K-NH2) with a single "guest" amino acid position.
• Assessed conformational propensities in aqueous 3-[N-morpholino]propane-sulfonic acid (MOPS) buffer.
• Evaluated propensities in non-micellar sodium dodecylsulfate (SDS) (protein interior-like) and micellar SDS, lysophosphatidylglycerol/lysophosphatidylcholine micelles (membrane-like).

Main Results:

• The study quantified the conformational propensity of each of the 20 amino acids across diverse environments.
• Significant environment-dependent variations in conformational propensity were observed for the amino acids.
• Hydrophobic interactions between peptide side chains and lipids were identified as key drivers of conformational changes in lipidic media.
• 65% of the amino acids showed significant environmental influence on their conformation when compared to literature data.

Conclusions:

• The conformational propensity of amino acids is highly dependent on their local environment.
• Investigating amino acid propensities in lipidic environments is essential for a comprehensive understanding of protein biological functions.
• The findings underscore the critical impact of local environmental factors on protein structural dynamics.