Atomic resolution structures of ribonuclease A at six pH values

Area of Science:

• Structural Biology
• Biochemistry
• Protein Crystallography

Background:

• Atomic resolution protein crystallography provides precise molecular structure insights.
• Understanding protein functionality requires studying subtle structural phenomena.

Purpose of the Study:

• To refine and compare six bovine pancreatic ribonuclease (RNase A) structures across a pH range.
• To investigate pH-triggered conformational changes and their impact on RNase A functionality.

Main Methods:

• X-ray diffraction analysis of protein crystals.
• Refinement of six RNase A structures at resolutions between 1.05-1.15 Å.
• Detailed stereochemical validation and comparative analysis of structural models.

Main Results:

• Six RNase A structures were refined at pH values 5.2 to 8.8.
• Stereochemical parameters suggest potential revisions to standard refinement targets.
• Experimental evidence highlights Lys41's role in catalysis and pH-dependent sulfate binding in the active site.

Conclusions:

• The study provides a detailed comparison of RNase A structures, elucidating pH-dependent conformational changes.
• Results support existing thermodynamic and kinetic data on RNase A folding and disulfide bridge function.
• Insights into catalytic mechanisms and substrate binding are offered.