Complete primary structure of bovine plasma fibronectin

Area of Science:

• Biochemistry
• Molecular Biology
• Proteomics

Background:

• Fibronectin is a crucial extracellular matrix glycoprotein involved in cell adhesion, migration, and wound healing.
• Understanding the primary structure of fibronectin is essential for deciphering its functional domains and interactions.
• Previous studies had partially elucidated fibronectin sequences, but a complete primary structure was lacking.

Purpose of the Study:

• To complete the primary structure of bovine plasma fibronectin.
• To identify and characterize splice variants and post-translational modifications.
• To compare the bovine sequence with homologous human fibronectin sequences.

Main Methods:

• Protein sequencing of specific peptide fragments of bovine plasma fibronectin.
• Analysis of carbohydrate groups and identification of free sulfhydryl groups.
• High-performance liquid chromatography (HPLC) for peptide mapping.
• Sequence homology comparisons with human fibronectin.

Main Results:

• The complete primary structure of 2265 residues of bovine plasma fibronectin was determined.
• Six type III homology units and two connecting strands were newly sequenced, totaling fifteen type III units.
• Evidence for two splice variants, similar to rat liver cells, was found; no 'extra' domain seen in human fibroblasts.
• Three new carbohydrate groups (two glucosamine-based, one galactosamine-based) were identified, totaling eight.
• A second free cysteine residue was located within a type III homology unit.
• HPLC analysis suggested an antiparallel interchain bridge pattern.
• High homology was observed between bovine plasma fibronectin and human cellular fibronectin sequences.

Conclusions:

• The complete primary structure of bovine plasma fibronectin provides a comprehensive molecular blueprint.
• The identified splice variants and post-translational modifications highlight fibronectin's complexity.
• The high sequence homology underscores conserved structural and functional aspects across species.