Occurrence of three novel alphas1-casein variants in goat milk
1997
Chianese, L. | Ferranti, P. | Garro, G. | Mauriello, R. (Universita di Napoli (Italy). Dipartimento di Scienza degli Alimenti) | Addeo, F.
In order to evaluate the quality of caprine milk from Italian breeds, individual samples were submitted to detailed casein analysis and attention focused mainly on alphas1-casein. Three novel variants were detected using gel electrophoretic techniques. The primary structure of three HPLC-purified alphas1-casein variants was determined with the aid of spectrometry techniques, for example electrospray mass spectrometry on intact protein, and fast atom bombardment in combination with Edman degradation on peptides to map the protein. Taking into account the present state of knowledge on alphas1-caprine polymorphism, the novel variants were labelled with the symbols H, I and L. The negative charge of the H variant was similar to that exhibited by the A variant, whereas the iso-electric point (pI) was lower, owing to the amino acid substitution Arg1(A)to Lys1(H) on the N-terminal residue. Taking into account the alphas1-casein level, the H variant was classified as a hard allele. Variant I presented similar values for pI and molecular mass, whereas the amino acid sequence was the same as that of alphas1-casein A, the only difference being that the I variant showed about half the amount of casein than the A variant. The L variant exhibited the highest anodic mobility among the alphas1-casein variants detected in caprine breeds up to now, a pI similar to that of the B2 variant, a single amino acid substitution Arg90 (B2) to His90 (L), and alphas1-casein expression similar to that of the "hard" alleles.
اظهر المزيد [+] اقل [-]الكلمات المفتاحية الخاصة بالمكنز الزراعي (أجروفوك)
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