The amino acid sequence of equine milk lysozyme.

The research article focuses on the determination and analysis of the amino acid sequence of equine milk lysozyme. The study reveals it is comprised of a single chain of 129 amino acids and bears some similarities but also significant differences to human milk lysozyme and domestic hen egg white lysozyme.

Methodology of the Research

The research process followed several steps:

• The study started with sequencing the N-terminal region of the complete protein. The N-terminal end of a protein is the initial part of the amino acid sequence.
• Cyanogen bromide fragments were then analyzed. Cyanogen bromide is a reagent which cleaves proteins at methionine residues, creating fragments that are simpler to analyze.
• Tryptic and chymotryptic peptides were also studied. These peptides are breakdown products of proteins which are created by the enzymes trypsin and chymotrypsin respectively.
• Chemical cleavage of the protein was performed after tryptophan residues resulting in more fragments for analysis.

Findings of the Research

The study discovered that:

• The equine milk lysozyme is made up of a single amino acid chain containing 129 residues. This translated to a Mr (relative molecular mass) of 14647.
• The equine milk lysozyme shares the basic characteristics of a c(chick)-type lysozyme, a group of lysozymes found in chicks and some other birds and mammals that play a role in fighting bacterial infections.
• However, the sequence has only a 51% match with that of human milk lysozyme and a 50% match with domestic hen egg white lysozyme. This indicates that despite being functionally similar, the proteins are not highly conserved at the amino acid sequence level.

Implications of the Findings

The paper discusses several important implications attributed to compelling differences in the sequence. Although it does not detail these implications, possible areas of significance might include:

• Differences in the structure or activity between equine, human, and hen lysozymes despite similar functions.
• Insights into the evolution of these proteins across different species.
• Opportunities for the development of species-specific drugs or treatments based on these variations.