Co-purification of proteases with basic fibroblast growth factor (FGF)

Area of Science:

• Biochemistry
• Molecular Biology
• Protein Chemistry

Background:

• Acidic and basic fibroblast growth factors (FGFs) are key signaling proteins involved in various cellular processes.
• FGFs exist in different molecular weight forms, with some higher molecular weight variants recently identified.
• Heparin-Sepharose chromatography is a common method for purifying FGF-related proteins due to their heparin-binding properties.

Purpose of the Study:

• To investigate the nature of 28-30 kDa components detected during the purification of acidic and basic FGFs.
• To determine if these higher molecular weight components are related to FGFs or represent other interacting proteins.
• To explore the potential role of these components in the observed microheterogeneity of FGFs.

Main Methods:

• Purification of acidic and basic FGFs from bovine pituitary glands using heparin-Sepharose chromatography.
• Immunoreactivity testing of eluted components against anti-basic FGF antisera.
• Microsequencing analysis to identify the protein composition of the 28-30 kDa fractions.

Main Results:

• Components of 28-30 kDa that were immunoreactive with anti-basic FGF antisera were detected during purification.
• Microsequencing analysis identified these 28-30 kDa components as lysosomal proteases.
• These lysosomal proteases co-eluted with basic FGF from heparin-Sepharose columns.

Conclusions:

• The higher molecular weight forms co-purifying with FGFs are not FGF variants but lysosomal proteases.
• These proteases may contribute to the microheterogeneity observed in FGF preparations.
• Further investigation is needed to understand the role of these proteases in FGF release and function.