Protein degradation in mammary gland explants. Evidence for limited heterogeneity of protein degradation rates.
Mammary gland explants in organ culture were subjected to hormonal manipulation, and rates of protein degradation during 1 and 2 day periods were measured by a double-isotope method. Isotope ratios for protein subunits in subcellular fractions were measured after resolution by two-dimensional polyacrylamide gel electrophoresis. Frequency distribution analysis shows that isotope ratios for each fraction are grouped predominantly in exponential distributions corresponding to populations of protein subunits with different mean degradation rates. The results also suggest that heterogeneity of protein degradation rates within each population is limited. There is no consistent correlation of degradation rate with protein isoelectric point or subunit molecular weight either overall or within any population of degradation rates. Therefore, the similarity of protein degradation rates within each population is clearly related to these molecular properties of the proteins.
D000818:Animals; D002250:Carbon Radioisotopes; D005260:Female; D007700:Kinetics; D008321:Mammary Glands, Animal / Q000378:metabolism*; D009924:Organ Culture Techniques; D011247:Pregnancy; D011506:Proteins / Q000378:metabolism*; D011817:Rabbits; D013347:Subcellular Fractions / Q000378:metabolism; D014316:Tritium
D002250:Carbon Radioisotopes; D011506:Proteins; D014316:Tritium