Rat serum factors inhibiting the G1-S transition in hepatocytes. II. Properties of the low molecular weight factor.
The properties were investigated of low molecular weight factors acting on the G1-S transition of baby rat hepatocytes. These factors were produced by incubating adult rat serum with trypsin or a 100,000 g liver microsomal fraction, and isolated by ultrafiltration. Enzyme degradation assays indicated that the active compound was in both cases a glycopeptide sensitive to pronase and papain and to the combination of neuraminidase and beta galactosidase. No loss of hepatocyte G1-S inhibitory activity was observed after heat treatment at pH 7.0. G50 gel filtration showed that both the G1-S inhibitory factors were collected in the last fractions eluted. The elution volume was slightly larger for the trypsin than for the microsomal-induced factor, suggesting a small difference between their molecular weight. These factors are believed to be glycopeptides with a molecular weight around 1400. They might be composed of a 3-sugar polysaccharide chain with a galactose preterminal and a neuraminic acid terminal, linked to a polypeptide chain of 6 to 8 amino acids.
D000818:Animals; D001798:Blood Proteins / Q000302:isolation & purification / Q000502:physiology*; D006020:Glycopeptides / Q000302:isolation & purification / Q000502:physiology*; D006601:Hexoses / Q000032:analysis; D006867:Hydrolases; D007399:Interphase; D008099:Liver / Q000502:physiology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D001798:Blood Proteins; D006020:Glycopeptides; D006601:Hexoses; D006867:Hydrolases