title: A novel whey protein synthesized only in late lactation by the mammary gland from the tammar (Macropus eugenii).
abstract: A major whey protein which appears in milk from the tammar wallaby (Macropus eugenii) only during the second half of lactation (late lactation protein-A, LLP-A) was purified to apparent homogeneity by ion-exchange chromatography and gel filtration. An Mr of 21,600 +/- 2000 was calculated from its amino acid composition. A computer-based comparison of the sequence of the first 69 amino acid residues with the Atlas of Protein Sequence data base showed no significant homology with known proteins. Antiserum to LLP-A was prepared in rabbits, and single radial immunodiffusion was used to measure the amounts of LLP-A in milk during the first 40 weeks of lactation. LLP-A was first detected at 26 weeks; thereafter its concentration increased abruptly, to reach a maximum of 26 g/l at approx. 36 weeks of lactation. Explants prepared from mammary gland biopsies at 20 and 35 weeks of lactation were exposed to [3H]amino acids for 8 h; immunoprecipitation of tissue extracts showed that, whereas the rate of casein synthesis was the same at both stages of lactation, LLP-A was synthesized only by the 35-week mammary gland.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005779:Immunodiffusion; D007774:Lactation / Q000378:metabolism*; D007614:Macropodidae / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008394:Marsupialia / Q000378:metabolism*; D008894:Milk Proteins / Q000096:biosynthesis* / Q000302:isolation & purification; D011247:Pregnancy; D013997:Time Factors; D000067816:Whey Proteins
chemical_list: D008894:Milk Proteins; D000067816:Whey Proteins