The serum proteome of Equus caballus.

This research article presents a study that successfully created a reference protein map for horse serum. The researchers were able to identify most proteins of moderate to high abundance through the application of different analytical techniques, such as two-dimensional electrophoresis and mass spectrometry, even though the horse genome is not completely characterized.

Construction of the Reference Protein Map

• The research started by separating serum proteins of the horse (Equus caballus) using a method known as two-dimensional electrophoresis (2-DE).
• Using 2-DE, 29 different gene products were detected and separated based on their electric charge and molecular weight. Each gene product corresponds to a unique protein, thus giving a preliminary view of the protein composition of the horse’s serum. This forms a reference protein map for further identification.

Protein Identification and Characterization

• A total of 29 proteins represented by 25 spots or spot groups on the 2-DE map were identified via different mass spectrometry techniques, such as tandem nanoelectrospray mass spectrometry (MS), matrix-assisted laser desorption ionization time-of-flight (TOF) MS, and a combination of both (TOF-TOF).
• These mass spectrometry methods provided high sensitivity and accuracy in detecting individual proteins. Their mass and structure were deduced from the data collected, which were then used for protein identification through comparison with existing protein databases – specifically, the human plasma protein database. Four proteins were identified this way because of their similarity to the known human proteins.
• For certain proteins like the immunoglobulins, immunoblotting technique, which uses specific antibodies that can recognise and bind to the targeted proteins, gave further information about their structure and function.

Observation of Protein Variants

• Albumin, a common protein in the serum, was identified both in its full-length form and in fragments of various sizes. This indicates that albumin undergoes some form of processing within the horse’s body which results in different versions of the protein appearing in the serum.
• Spots representing different versions of other proteins such as alpha1-antitrypsin, haptoglobin, and transthyretin were also observed. These proteins showed differences in mass and electric charge, suggesting that they may undergo modifications after their initial production in the horse’s body.

Conclusion

• The research provides a comprehensive reference of the serum protein map of the Equus caballus.
• Despite the incomplete characterization of the Equus caballus genome, the study was able to identify and characterize most of the moderate to high abundance proteins stained in the serum 2-DE pattern.
• These findings significantly contribute to the existing knowledge about the horse’s biology and can be used in future research to further understand how these proteins function in health and disease states.