The carbohydrate side chains of the major plasma serpins of horse and wallaby: analyses of enzymatic and chemically treated (including ‘Smith degradation’) protein blots by lectin binding.

This study investigates the sugar attachments or carbohydrate side chains of the major plasma serpins (proteins with serine protease inhibitory activity) in horses and wallabies. The researchers used a variety of chemical and enzymatic methods to identify the structures of these chains, comparing them to a commonly studied human serpin. They found notable differences in these side chains between species.

Research Methodology

• The researchers analysed the carbohydrate side chains of major plasma serpins found in horses and wallabies, using the major human plasma serpin, alpha 1-protease inhibitor, as a control for comparison.
• The process involved running protein blots from two-dimensional gels. These gels allow for visualizing proteins based on their charge and size.
• The blot was then treated with eight different lectins, which are proteins that bind to specific carbohydrate structures to help identify them.
• The protein blots were also treated with several methods to reveal the structure of the carbohydrate side chains. These included enzymatic deglycosylation (removal of sugar groups), chemical methods to remove sialic acid and fucose (types of sugars), and a technique called ‘Smith degradation’.

Results

• With the assumption of a standard complex side chain structure for comparison, the results of the 21 possible combinations of lectin treatments were interpreted to provide information about the carbohydrate side chains on the equine and wallaby proteins.
• The researchers found that most equine proteins consisted of partially sialylated biantennary side chains, except for the most acidic proteins which had triantennary side chains. These terms refer to the structure of the side chains, with ‘biantennary’ indicating two antenna-like extensions from the main chain, ‘triantennary’ meaning three extensions, and ‘sialylated’ indicating the addition of sialic acid.
• The wallaby proteins had both bi- and triantennary side chains. However, they also had a distinguishing feature, a N-acetylglucosamine and fucose residue. These sugar molecules were found to attach in a ‘bisecting’ manner (fitting between two parts).

Conclusion

• This investigation provides a detailed comparison of the carbohydrate side chains of equine, wallaby, and human serpins. While the study gives valuable insights into these proteins within each species, their differences may also be significant for understanding the evolution and functioning of serpins across different animals.