Small angle X-ray scattering study of S100 proteins

Area of Science:

• Biochemistry
• Structural Biology
• Biophysics

Background:

• S100 proteins are a family of calcium-binding proteins involved in various cellular processes.
• Understanding the oligomeric state and structural dynamics of S100 proteins is crucial for elucidating their functions.
• Previous studies have suggested diverse oligomeric states for S100 proteins, necessitating further structural investigation.

Purpose of the Study:

• To investigate the oligomeric state and structural characteristics of S100b and a mixture of S100a and S100ao (S100a,ao) proteins.
• To determine the effect of trifluoroperazine (TFP) on the aggregation and structure of S100 proteins.
• To compare the structural differences between S100b and S100a,ao dimers.

Main Methods:

• Small-angle X-ray scattering (SAXS) was employed to analyze protein structure.
• Experiments were conducted over a protein concentration range of 1.5 to 10.0 mg/ml.
• The influence of trifluoroperazine (TFP) at a molar ratio of 1 TFP per protein dimer was assessed.

Main Results:

• SAXS measurements indicated that S100b and S100a,ao proteins predominantly exist as dimers under the studied conditions.
• The addition of TFP effectively suppressed higher-order aggregation of S100 proteins.
• The radius of gyration for S100b dimers was determined to be 19.5 ± 0.3 Å, while for S100a,ao dimers it was 20.2 ± 0.3 Å.
• A statistically significant difference in the radius of gyration (0.7 ± 0.3 Å) was observed between S100b and S100a,ao dimers.

Conclusions:

• S100b and S100a,ao proteins primarily form dimers in solution.
• Trifluoroperazine acts as an inhibitor of S100 protein aggregation.
• The distinct radii of gyration suggest that S100b and S100a,ao dimers possess different, asymmetrical structures.