Identification and the primary structure of equine alpha-lactalbumin B and C (Equus caballus, Perissodactyla).

This research describes the identification and structural analysis of two new alpha-lactalbumins, B and C, found in the colostrum of a Persian Arab mare. The structures were compared with a previously isolated alpha-lactalbumin, A, from Australian horses as well as from bovine lactalbumin B. The study also discusses the structure-function relationship and calcium binding sites of alpha-lactalbumin.

Study Details

• The researchers worked on colostrum sourced from a single Persian Arab mare and managed to identify the presence of two new alpha-lactalbumins. Alpha-lactalbumins are proteins present in the milk of almost all mammalian species, playing a crucial role in the regulation of milk production. These newly discovered alpha-lactalbumins were named equine alpha-lactalbumin B and C.
• They compared these newly discovered proteins with a previously isolated protein from the milk of Australian horses (English Thoroughbred), known as alpha-lactalbumin A.

Protein Structure Analysis

• To determine the primary structures of the newly discovered alpha-lactalbumin B and C, the researchers utilised a method called automatic Edman degradation which is a stepwise process to sequence proteins.
• The oxidative cleavage of the proteins was carried out using enzymes. Further, cyanogen bromide was used for the cleavage of S-carbamoyl-methylated protein, which provided overlapping peptides that could help in sequencing the protein.
• The resulting sequences of alpha-lactalbumin B and C were then compared to alpha-lactalbumin A. This comparison revealed that there were 3 and 4 amino acid exchanges respectively, meaning there were slight differences in the structure of these proteins.
• The researchers made further comparisons, this time with bovine alpha-lactalbumin B, revealing greater differences. The results indicated that there were 39 and 40 amino acid exchanges respectively for equine alpha-lactalbumin B/C, suggesting a significant variation in the protein structure when compared to a different species.

Discussion on Structure-Function Relationship

• The paper also presented a discussion on the structure-function relationship of alpha-lactalbumin, which essentially refers to how the specific structure of these proteins influences their functionality.
• The researchers talked about the calcium binding sites of alpha-lactalbumin. Calcium is an essential mineral for many metabolic processes and it’s binding to these proteins could affect their structure and function.
• The various variants of alpha-lactalbumin, possibly resulting from the slight differences in amino acid composition, were also discussed in the study.

In conclusion, the study provides valuable insights into the structure and functionality of newly discovered alpha-lactalbumin B/C in equine species. The differences in structure compared to previously identified alpha-lactalbumin A and bovine lactalbumin B could have implications on their functionality and role in various metabolic processes.