Characterization of rabbit surfactant-associated proteins

Area of Science:

• Biochemistry
• Pulmonary Biology

Background:

• Pulmonary surfactant is crucial for lung function.
• The protein components (apolipoproteins) of surfactant are less understood than its lipid components.

Purpose of the Study:

• To characterize the apolipoproteins associated with purified rabbit lung surfactant.
• To determine the complexity and nature of surfactant-associated proteins.

Main Methods:

• Purification of surfactant from adult rabbit lung lavage.
• Assessment of surfactant purity via glycerophospholipid analysis and electron microscopy.
• Delipidation of surfactant followed by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) for apolipoprotein analysis.

Main Results:

• At least eight distinct apolipoproteins or protein families were identified in purified surfactant.
• Four apolipoprotein families (55-70, 29-36, 26-28, 22-23 kDa) exhibited acidic isoelectric points and bound to Concanavalin A-Sepharose, indicating glycosylation.
• Neuraminidase treatment suggested sialic acid presence in the 29-36 kDa family. A 66 kDa protein was identified as likely albumin.

Conclusions:

• Rabbit lung surfactant contains a more complex and diverse array of apolipoproteins than previously recognized.
• Glycosylation and sialic acid residues are present on some surfactant apolipoproteins.
• The characterization of these proteins provides a foundation for understanding their roles in surfactant structure and function.