New data on the proteins of rabbit (Oryctolagus cuniculus) milk (original) (raw)

1995, Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology

The main rabbit milk proteins have previously been prepared by reversed-phase HPLC of the acid-precipitated material ('whole casein') and of its supernatant (acid whey). Most of them were nearly homogeneous on SDS-PAGE. Among those isolated from whole casein, ~st-, P-and g-caseins, as well as whey acidic protein (WAP) were identified by N-terminal sequencing. After further internal sequencing, two unknown proteins were found to be the putative products, ~a-and ~s2b-caseins of two recently sequenced transcripts from rabbit mammary gland. Each whole casein component gave several bands on IEF. For K-casein, this was probably due to uneven glycosylation as in all g-caseins studied so far. For the other whole casein components, including WAP, the number of bands roughly reflected the number of potential phosphorylation sites predicted from the sequences. For ~st-and ~2-caseins polymorphism could be detected. From acid whey, in addition to WAP, which was a minor component, reversed phase HPLC separated three proteins. These were ~-lactalbumin, transferrin and serum albumin, on the basis of their apparent molecular weights deduced from SDS-PAGE. WAP was a major component of the native whey obtained by ultracentrifugation of rabbit milk. It was found to consist of two identical subunits linked by at least one disulfide bridge.

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