The genetic variations in CSN2 gene of Indian sheep breeds affect its protein stability and function

Abstract

Milk from minor dairy animals, such as sheep and goats, is gaining popularity, and its quality is viewed as significant in light of current healthy dietary trends. The β-casein (coded by CSN2 gene) is the most abundant casein protein family member accounting for more than half of the total casein protein in sheep milk. The goal of this work was to find genetic polymorphism (SNP) in the sheep CSN2 gene and predict how SNPs will affect protein stability and function. The mRNA was isolated from milk somatic cells of nine sheep breeds from northern India to get the complete coding β-casein gene. The exon seven of β-casein was screened for the genetic variations at DNA level by PCR-SSCP method, from 300 sheep belonging to nine breeds. The comparative sequence analysis in Indian sheep breeds revealed 21 novel CSN2 protein variants, maximum of the variants raised due to the SNPs in the exon seven of the gene. The computational analysis of deduced amino acids substitutions in CSN2 protein demonstrated that these changes in the mature protein could change the structure, stability and function of the milk protein. Variations in the signal peptide and mature protein sequences were projected to have a negative impact on the casein protein's stability and function. These changes were also projected to disrupt CSN2 protein post-translational modifications, which could affect different technical aspects of milk, thereby jeopardizing crucial milk coagulation features like rennet coagulation time and curd hardness.