Vanadate inhibits the ATP-dependent degradation of proteins in reticulocytes without affecting ubiquitin conjugation

Journal Article · Thu Mar 01 00:00:00 EST 1984 · J. Biol. Chem.; (United States)

OSTI ID:6444140

Tanaka, K; Waxman, L; Goldberg, A L

Reticulocytes contain a nonlysosomal, ATP-dependent system for degrading abnormal proteins and normal proteins during cell maturation. Vanadate, which inhibits several ATPases including the ATP-dependent proteases in Escherichia coli and liver mitochondria, also markedly reduced the ATP-dependent degradation of proteins in reticulocyte extracts. At low concentration (K/sub I/ = 50 ..mu..M), vanadate inhibited the ATP-dependent hydrolysis of (/sup 3/H)methylcasein and denatured /sup 125/I-labeled bovine serum albumin, but it did not reduce the low amount of proteolysis seen in the absence of ATP. This inhibition by vanadate was rapid in onset, reversed by dialysis, and was not mimicked by molybdate. Vanadate inhibits proteolysis at an ATP-stimulated step which is independent of the ATP requirement for ubiquitin conjugation to protein substrates. When the amino groups on casein and bovine serum albumin were covalently modified so as to prevent their conjugation to ubiquitin, the derivatized proteins were still degraded by an ATP-stimulated process that was inhibited by vanadate. In addition, vanadate did not reduce the ATP-dependent conjugation of /sup 125/I-ubiquitin to endogenous reticulocyte proteins, although it markedly inhibited their degradation. In intact reticulocytes vanadate also inhibited the degradation of endogenous proteins and of abnormal proteins containing amino acid analogs. This effect was rapid and reversible; however, vanadate also reduced protein synthesis and eventually lowered ATP levels in the intact cells. Vanadate (10 mM) has also been reported to decrease intralysosomal proteolysis in hepatocytes. However, in liver extracts this effect on lysosomal proteases required high concentrations of vanadate (K/sub I/ = 500 ..mu..M) and was also observed with molybdate, unlike the inhibition of ATP-dependent proteolysis in reticulocytes.

• Research Organization: Harvard Medical School, Boston, MA
• OSTI ID: 6444140
• Journal Information: J. Biol. Chem.; (United States), Vol. 259:4
• Country of Publication: United States
• Language: English

Related Subjects

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
PROTEINS
DECOMPOSITION
VANADATES
BIOLOGICAL EFFECTS
ATP
ENZYMES
INHIBITION
PROTEOLYSIS
RETICULOCYTES
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BODY FLUIDS
CHEMICAL REACTIONS
ERYTHROCYTES
MATERIALS
NUCLEOTIDES
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
560301* - Chemicals Metabolism & Toxicology- Cells- (-1987)