Biochemical and molecular characterization of polymorphisms of αs1-casein in Sudanese camel (Camelus dromedarius) milk

This work was designed to detect occurrence of biochemical polymorphism of αs1-casein in two ecotypes of Sudanese camel (Camelus dromedarius) and to characterize these variants on molecular level. Milk samples were screened for αs1-casein variability by isoelectric focusing, using skimmed milk, as well as isolated αs1-casein. Two protein patterns, named αs1-casein A and C, were identified, whereas the major allele A revealed frequencies of 0.8214 and 0.8615 in the two ecotypes. CSN1S1*A and CSN1S1*C are both characterized by missing of exon 16 on mRNA-level compared with the previously described CSN1S1*B. However, the sequence of exon 16 occurs on DNA-level in both. Therefore, this exon seems to be skipped out during mRNA-processing. Furthermore, CSN1S1*C shows a single G > T nucleotide substitution in exon 5, leading to a non-synonymous amino acid exchange (p.Glu30 > Asp30; GenBank ID: JF429138). A polymerase chain reaction-restriction fragment length polymorphism-method was established as a DNA-based test for this nucleotide substitution.