title: A soluble ATP-dependent proteolytic system responsible for the degradation of abnormal proteins in reticulocytes.
abstract: Reticulocytes, like other cells, selectively degrade certain abnormal proteins by an energy-dependent process. When isolated rabbit reticulocytes incorporate the valine analog 2-amino-3chlorobutyric acid (ClAbu) in place of valine, they produce an abnormal globin that is degraded with a half-life of 15 min. Normal hemoglobin, in contrast, undergoes little or no breakdown within these cells. Cell-free extracts from reticulocytes have been shown to rapidly hydrolyze these abnormal proteins. The degradative system is located in the 100,000 X g supernatant, has a pH optimum of 7.8, and does not appear to be of lysosomal origin. This breakdown of analog-containing protein was stimulated severalfold by ATP, and slightly by ADP. AMP and adenosine-3':5'-cyclic monophosphate had no significant effect on proteolysis. Experiments with ATP analogs suggest that the terminal high energy phosphate is important in the degradative process. Proteolysis in the cell-free system and in intact reticulocytes was inhibited by the same agents (L-l-tosylamido-2-phenyl-ethylchloromethyl ketone, N-alpha-p-tosyl-L-lysine chloromethyl ketone, N-ethylmaleimide, iodoacetamide, and o-phenanthroline). In addition, the relative rates of degradation of several polypeptides in the cell-free extracts paralleled degradatives rates within cells. Thus, a soluble nonlysosomal proteolytic system appears responsible for the energy-dependent degradation of abnormal proteins in reticulocytes.
mesh_terms: D000255:Adenosine Triphosphate / Q000097:blood*; D000818:Animals; D001798:Blood Proteins / Q000378:metabolism*; D002474:Cell-Free System; D005914:Globins / Q000378:metabolism; D010447:Peptide Hydrolases / Q000097:blood*; D010455:Peptides / Q000097:blood*; D010618:Phenanthrolines / Q000494:pharmacology; D011480:Protease Inhibitors; D011691:Puromycin; D011817:Rabbits; D012156:Reticulocytes / Q000201:enzymology / Q000378:metabolism*; D012995:Solubility; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D014108:Tosylphenylalanyl Chloromethyl Ketone / Q000494:pharmacology; D014633:Valine / Q000031:analogs & derivatives / Q000097:blood
chemical_list: D001798:Blood Proteins; D010455:Peptides; D010618:Phenanthrolines; D011480:Protease Inhibitors; D013439:Sulfhydryl Reagents; D014108:Tosylphenylalanyl Chloromethyl Ketone; D011691:Puromycin; D000255:Adenosine Triphosphate; D005914:Globins; D010447:Peptide Hydrolases; D014633:Valine
references.citation: Biochim Biophys Acta. 1964 Oct 16;91:313-22
references.pmid: 14240649
references.citation: J Biol Chem. 1975 Mar 10;250(5):1694-701
references.pmid: 1112824
references.citation: J Biol Chem. 1972 May 25;247(10):3341-52
references.pmid: 4554917
references.citation: Proc Natl Acad Sci U S A. 1972 Sep;69(9):2640-4
references.pmid: 4560693
references.citation: Science. 1973 Apr 6;180(4081):33-9
references.pmid: 4144403
references.citation: FEBS Lett. 1974 Apr 1;40(2):297-301
references.pmid: 4369108
references.citation: J Biol Chem. 1969 Oct 25;244(20):5713-23
references.pmid: 4310604
references.citation: Biochem J. 1976 Jun 15;156(3):609-17
references.pmid: 182157
references.citation: Annu Rev Biochem. 1974;43(0):835-69
references.pmid: 4604628
references.citation: Biochem J. 1972 Jul;128(4):763-9
references.pmid: 4629422
references.citation: Adv Enzymol Relat Areas Mol Biol. 1975;43:1-56
references.pmid: 890
references.citation: J Biol Chem. 1972 Jul 10;247(13):4107-13
references.pmid: 4556303
references.citation: Annu Rev Microbiol. 1972;26:103-26
references.pmid: 4562805
references.citation: Annu Rev Biochem. 1976;45:747-803
references.pmid: 786161
references.citation: J Biol Chem. 1975 Jun 10;250(11):4278-84
references.pmid: 805138
references.citation: J Biol Chem. 1975 Feb 10;250(3):1112-22
references.pmid: 1089651
references.citation: J Biol Chem. 1976 Jun 25;251(12):3521-9
references.pmid: 931997
references.citation: Ann N Y Acad Sci. 1969 Nov 20;165(1):212-20
references.pmid: 5260144