The composition, structure and origin of proteose-peptone component 8F of bovine milk.
Proteose-peptone component 8F (or '8-fast') has been prepared from bovine milk. Sedimentation equilibrium analysis, polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate and gel filtration in urea-containing buffers all gave molecular weight values between 3300 and 3900. The N-terminal sequence was found to be Arg-Glu- by dansylation and Edman degradation. Hydrazinolysis released lysine from the C-terminus. A mixture of carboxypeptidases A and B showed that the C-terminal sequence was -Thr-(Arg,Ile,Asn)-Lys. The phosphate content was 3.8 mol/mol and was completely released by a short alkaline hydrolysis indicating linkage to serine. This and all other aspects of the composition were entirely consistent with the identification of this proteosepeptone as residues 1--28 of the beta-casein molecule. This identity was confirmed by a peptide mapping procedure. Thus proteose-peptone component 8F represents the N-terminal fragment when the gamma1-caseins are formed by proteolysis of beta-casein.
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002268:Carboxypeptidases / Q000378:metabolism; D002417:Cattle; D005260:Female; D007700:Kinetics; D008892:Milk / Q000032:analysis; D008894:Milk Proteins / Q000302:isolation & purification; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis
D000596:Amino Acids; D008894:Milk Proteins; D010446:Peptide Fragments; D002268:Carboxypeptidases