Two plasma fibronectin fragments with different gelatin-binding properties

Area of Science:

• Biochemistry
• Molecular Biology

Background:

• Human plasma fibronectin is a large glycoprotein involved in cell adhesion and matrix assembly.
• Fibronectin's gelatin-binding domains are crucial for its interactions with extracellular matrix components.

Purpose of the Study:

• To investigate the differential gelatin affinities of subtilisin-generated fibronectin fragments.
• To characterize the heparin-binding properties of these fibronectin fragments.

Main Methods:

• Enzymatic digestion of human plasma fibronectin using subtilisin.
• Affinity chromatography on gelatin-Sepharose.
• Urea gradient elution to assess binding strength.
• Amino-terminal sequencing to identify fragment origins.

Main Results:

• Two distinct fibronectin fragments (60 kDa and 40 kDa) were generated.
• The 60 kDa fragment exhibited lower gelatin affinity, eluting under specific buffer conditions, while the 40 kDa fragment remained bound.
• The 60 kDa fragment demonstrated heparin-binding activity.
• Identical amino-terminal sequences confirmed the 40 kDa fragment is derived from the 60 kDa fragment, with heparin-binding located in the carboxyl-terminal region.

Conclusions:

• Subtilisin cleavage generates fibronectin fragments with differential gelatin affinities.
• The 60 kDa fragment contains a heparin-binding site within its carboxyl-terminal region, distinct from the primary gelatin-binding domains.