Fibronectin in extended and compact conformations. Electron microscopy and sedimentation analysis

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Fibronectin is a key extracellular matrix protein involved in cell adhesion, migration, and differentiation.
• Its conformation is known to change in response to environmental factors, but the precise mechanisms are not fully understood.

Purpose of the Study:

• To investigate the ionic strength-dependent conformational changes of fibronectin.
• To determine whether these changes occur independently within fibronectin half-molecules.
• To elucidate the molecular interactions driving fibronectin's conformational transitions.

Main Methods:

• Zone sedimentation in glycerol gradients to assess molecular conformation.
• Analysis of intact fibronectin, reduced and carboxyamidomethylated half-molecules, and proteolytic fragments.
• Electron microscopy to visualize structural changes.

Main Results:

• Fibronectin exhibited distinct sedimentation coefficients at different ionic strengths, indicating conformational changes.
• Half-molecules showed independent conformational shifts, suggesting localized interactions.
• Electron microscopy revealed extended strands at high ionic strength and irregularly coiled structures at low ionic strength.

Conclusions:

• Fibronectin's conformational changes are primarily driven by short-range electrostatic interactions along the molecule.
• These interactions lead to increased bending and coiling of the fibronectin strand at low ionic strength.
• The findings provide insights into the dynamic nature of fibronectin and its role in cellular processes.