Statistical conformation of human plasma fibronectin

Area of Science:

• Biophysics
• Biochemistry
• Extracellular Matrix Biology

Background:

• Fibronectin is a crucial glycoprotein in the extracellular matrix (ECM) involved in cell adhesion.
• The precise conformation of fibronectin under physiological conditions is not well understood.
• Understanding fibronectin's structure is vital for comprehending ECM organization and cellular processes.

Purpose of the Study:

• To investigate the conformation of fibronectin in its native state using scattering techniques.
• To determine the structural characteristics of fibronectin and compare them to globular and unfolded proteins.
• To elucidate the implications of fibronectin's native conformation on ECM structure and function.

Main Methods:

• Static Light Scattering (SLS) and Small-Angle Neutron Scattering (SANS) to determine the radius of gyration (Rg).
• Quasi-Elastic Light Scattering (QELS) to measure the hydrodynamic radius (RH).
• Analysis of scattering data to model fibronectin's shape and compare it to theoretical models.

Main Results:

• Native fibronectin exhibits a radius of gyration (Rg) of 15.3 nm and a hydrodynamic radius (RH) of 11.5 nm.
• The ratio RH/Rg (0.75) suggests a Gaussian chain-like conformation, distinct from globular proteins.
• Denaturation with 8 M urea increased Rg by a factor of 2, indicating the native state is not fully unfolded.
• SANS data is consistent with a random string model of 56 beads, ruling out globular or completely unfolded states.

Conclusions:

• Fibronectin in its native state possesses a conformation best described as a flexible, Gaussian chain.
• This conformation is neither fully unfolded nor a compact globular structure.
• The determined structure has significant implications for the organization and mechanics of the extracellular matrix.