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Phosphorylation of mammalian initiation factor eIF-4B

Conference · · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)
OSTI ID:6065716
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The phosphorylation of initiation factors appears to be an important mechanism for regulating the rate of translation in mammalian cells. eIF-4B (80 kDa) purified from HeLa cells exhibits a complex array of 8 to 12 spots when analyzed by 2-dimensional isoelectric focusing - SDS polyacrylamide gel electrophoresis. A similar array of eIF-4B spots is seen when total lysate proteins are analyzed by immunoblotting with anti-eIF-4B antiserum or with antibodies affinity-purified from the most basic eIF-4B spot. The multiple forms of eIF-4B are due to phosphorylation, since all but the most basic spot are labeled with (/sup 32/P)phosphate in vivo and the action of alkaline phosphatase in vitro reduces the array to only two spots. Tryptic peptide maps of phosphopeptides from each of the various isoelectric variants of eIF-4B show a similar complexity, suggesting that a number of different sites are phosphorylated in a random order. When serum-deprived HeLa cells are treated with phorbol ester, both the protein synthesis rate and the extent of eIF-4B phosphorylation increase, suggesting that C kinase may be a regulator of translation. Purified C kinase phosphorylates a number of pure initiation factors in vitro, but eIF-4B is the strongest target protein. When pure eIF-4B is treated, the entire mass of eIF-4B is shifted to the most acidic spots, indicating very strong phosphorylation. Attempts are being made to detect differences in the in vitro activities of the non-phosphorylated and highly phosphorylated forms.

Research Organization:
Univ. of California, Davis
OSTI ID:
6065716
Report Number(s):
CONF-870644-
Journal Information:
Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Vol. 46:6; ISSN FEPRA
Country of Publication:
United States
Language:
English

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Related Subjects

550201 -- Biochemistry-- Tracer Techniques
560300* -- Chemicals Metabolism & Toxicology
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ALKALINE PHOSPHATASE
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
CARCINOGENS
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
ELECTROPHORESIS
ENZYME ACTIVITY
ENZYMES
ESTERASES
ESTERS
GENETIC MAPPING
HELA CELLS
HYDROLASES
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MAPPING
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PHORBOL ESTERS
PHOSPHATASES
PHOSPHATES
PHOSPHORUS 32
PHOSPHORUS COMPOUNDS
PHOSPHORUS ISOTOPES
PHOSPHORUS-GROUP TRANSFERASES
PHOSPHORYLATION
PHOSPHOTRANSFERASES
PROTEINS
RADIOISOTOPES
TRACER TECHNIQUES
TRANSFERASES