Conformational changes in calcium-sensor proteins under molecular crowding conditions

Area of Science:

• Biochemistry
• Molecular Biology
• Biophysics

Background:

• Signaling pathways rely on switch proteins that regulate signal transduction.
• Calcium (Ca2+) sensor proteins are crucial switch proteins, altering conformation based on intracellular Ca2+ levels.

Purpose of the Study:

• To compare the protein dynamics of various Ca2+-binding proteins under molecular crowding conditions.
• To investigate how Ca2+ sensor proteins exhibit distinct conformational changes and hydrodynamic properties.

Main Methods:

• Utilized dynamic light scattering (DLS) and surface plasmon resonance (SPR) biosensor technology.
• Monitored conformational changes of calmodulin, troponin C, recoverin, and guanylate cyclase-activating protein (GCAP).
• Analyzed protein dynamics under varying Ca2+ concentrations and molecular crowding.

Main Results:

• SPR provided unique fingerprint profiles for each Ca2+-sensor protein, sensitive to Ca2+ levels and point mutations.
• Conformational changes correlated with alterations in hydrodynamic size, hydration shell, and protein-water interface dielectric properties.
• SPR and DLS data showed strong correlation, validating the assessment of protein dynamics.

Conclusions:

• Ca2+ sensor proteins, despite similar structures, exhibit distinct Ca2+-dependent functional states under crowding.
• SPR is a powerful tool for characterizing protein conformational dynamics and hydration shell rearrangements.
• Understanding these differences is key to deciphering diverse signal transduction events.