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W B Benjamin

Publications and source records attributed to W B Benjamin.

30 records · Page 2Linked to original sources
PubMed1981

Evidence for an essential arginine residue at the active site of ATP citrate lyase from rat liver.

Rat liver ATP citrate lyase was inactivated by 2, 3-butanedione and phenylglyoxal. Phenylglyoxal caused the most rapid and complete inactivation of enzyme activity in 4-(2-hydroxyethyl)-1-piperazine-ethanesulphonic acid buffer, pH 8. Inactivation by both butanedione and phenylglyoxal was concentration-dependent and followed pseudo- first-order kinetics. Phenylglyoxal also decreased autophosphorylation (catalytic phosphate) of ATP citrate lyase. Inactivation by phenylglyoxal and butanedione was due to the modification of enzyme arginine residues: the modified enzyme failed to bind to CoA-agarose. The V declined as a function of inactivation, but the Km values were unaltered. The substrates, CoASH and CoASH plus citrate, protected the enzyme significantly against inactivation, but ATP provided little protection. Inactivation with excess reagent modified about eight arginine residues per monomer of enzyme. Citrate, CoASH and ATP protected two to three arginine residues from modification by phenylglyoxal. Analysis of the data by statistical methods suggested that the inactivation was due to modification of one essential arginine residue per monomer of lyase, which was modified 1.5 times more rapidly than were the other arginine residues. Our results suggest that this essential arginine residue is at the CoASH binding site.

ATP Citrate (pro-S)-Lyase↗
PubMed1979

Fat cell protein phosphorylation. Identification of phosphoprotein-2 as ATP-citrate lyase.

We have purified to apparent homogeneity a phosphoprotein from rat adipose tissue which is rapidly phosphorylated in vitro by ATP. The native phosphoprotein has an approximate sedimentation coefficient of 14.8 S. On sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis, the protein dissociated into identical subunits of Mr = 128,000. A phosphoprotein with similar properties was also isolated from liver. Purified phosphoproteins from fat cells and liver had ATP-citrate lyase activity and co-migrated on sodium dodecyl sulfate gels with fat cell phosphoprotein-2, the phosphorylation of which is increased by incubating fat cells with insulin. The phosphoamino acid residue of the cells with insulin. The phosphoamino acid residue of the phosphoprotein was identified as tau-phosphohistidine. These evidences suggest that fat cell phosphoprotein-2 is ATP-citrate lyase.

ATP Citrate (pro-S)-Lyase↗
PubMed1976

The effect of ecdysterone on nonhistone proteins in salivary gland chromosomes of Sciara coprophila.

Synthesis and transport of proteins to the cell nucleus during puff induction was studied in S. coprophila. Changes in grain distribution along chromosomes (L-methionine [35S] incorporation into protein) were correlated with puffs induced by ecdysterone in vitro; A pattern of specific labelling at the sites of incipient puffs was noted within 2 h after the addition of the hormone, i.e. grains on the chromosomes were in clusters, characteristic for this time point and not seen in the controls (where only non-specific labeling was noted 0-4 h). Characteristic chromosomal puffs appeared between 3-4 h after the addition of ecdysterone. It was concluded that during ecdysterone-induced puff formation in salivary gland chromosomes, proteins which had been previously synthesized were selectively transported from the cytoplasm to specific sites on the chromosomes.

Animals↗
PubMed1975

Actions of insulin, epinephrine, and dibutyryl cyclic adenosine 5'-monophosphate on fat cell protein phosphorylations. Cyclic adenosine 5'-monophosphate dependent and independent mechanisms.

Endogenous and hormone-induced protein (polypeptide) phosphorylations were studied in isolated rat fat cells, in fat pads, and in subcellular fractions obtained from fat tissue under different physiological conditions. Insulin (25-100 muU/ml) increased the incorporation of 32P into two proteins: insulin-phosphorylated proteins (IPP 140 and IPP 50; similar to 140,000 and 50,000 daltons, respectively). Epinephrine (10(-7)-10(-6) M) increased the incorporation of 32P into another protein: epinephrine-phosphorylated protein (EPP 60-65; similar to 60,000-65,000 daltons). Endogenous IPP 140 phosphorylation in fat cells obtained from fasted and refed rats was similar to that of insulin in normal cells. Studies of insulin and epinephrine interactions showed that insulin increased IPP 140 phosphorylation even in the presence of epinephrine or lithium (25 mM times 10(-3) M). dibutyryl cyclic AMP (5 times 10(-4) M) markedly stimulated EPP 60-65 phosphorylation, but neither epinephrine (10(-7)-10(-6) M) nor dibutyryl cyclic AMP reproduced insulin's phosphorylation of APP 140. Lithium inhibited both endogenous and epinephrine-stimulate EPP 60-65 phosphorylation, but did not inhibit that induced by dibutyryl cyclic AMP. These findings suggest that insulin stimulated a specific, cyclic AMP independent protein kinase for IPP 140 phosphorylation. Cell-free extracts from insulin-treated fat tissue catalyzed the specific transfer of 32P from ATP to IPP 140 more rapidly than control extracts. No differences in the total receptor protein or total protein kinase activity using [gamma(-32P]ATP were noted between insulin-treated and control preparations. IPP 140 may be either (a) an insulin-sensitive protein kinase (phosphotransferase) or (b) a protein whose function is regulated by an insulin-sensitive protein kinase or phosphatase.

Adipose Tissue↗
PubMed1974

Aldosterone-induced protein in toad urinary bladder.

Simultaneous electrophysiological and biochemical experiments demonstrated a specific aldosterone-induced protein in paired urinary hemibladders isolated from the toad Bufo marinus. Whenever aldosterone stinlmulated short-circuit current, aldosterone specifically increased [(35)S] methionine incorporation into a low-molecular-weight protein (about 12,000). Comparative studies with dexamethasone and insulin and inhibitory studies with spironolactone and actinomycin D suggest mineralocorticoid specificity.

Aldosterone↗
PubMed1969

Phosphorylation of dipteran chromosomes and rat liver nuclei.

Side-chain modifications of the nucleoproteins are believed to be involved in the control of gene function. Rat liver nuclei and chromatin incubated in adenosine triphosphate labeled in the gamma position with phosphorus-32 demonstrated rapid phosphorylation in vitro of the nuclear proteins. Dipteran salivary glands incubated in either labeled adenosine triphosphate or ortho-phosphate labeled with phosphorus-32 showed that there is phosphorylation of chromosomal protein. The phosphorus is associated in protein from both liver and salivary gland nuclei predominantly with phosphoserine.

Adenosine Triphosphate↗