Identification of the variant C of β-lactoglobulin in sheep using a polymerase chain reaction-restriction fragment length polymorphism method

β-Lactoglobulin (β-LG) is the major whey protein in the milk of ruminants and is able to bind and transport small hydrophobic molecules. However, its biological role is mainly unknown (G odovac -Z immermann 1988). Previously three genetic variants have been found in sheep: A, B and C. The genetic variants A and B differ at amino acid position 20, where variant A has a His and variant B has a Thr (K olde and B raunitzer 1983). The variant C is a subtype of variant A with a single amino acid exchange of Arg→Glu at position 148 (E rhardt et al. 1989). The genotype β-LG BB was found to be associated with higher milk yield, whereas genotypes AA and AB had a higher milk protein and casein content as well as yielding more curd (G arzon and M artinez 1992). No data is available concerning the relationship between the β-LG C allele and production traits or milk properties. Since DNA-based genotyping has already been performed for alleles A and B (S chlee et al. 1993), the aim of the present study was to develop a DNA-based method for identifying the β-LG C variant. However polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) typing has been established (P rinzenberg and E rhardt 1999) recently, and this study shows an alternative method to detect β-LG C.