scholarly journals Decreased activity of peptide-elongation factors after treatment with cholesterol esterase

1978 ◽  
Vol 172 (1) ◽  
pp. 9-13 ◽  
Author(s):  
J Hradec ◽  
Z Tuháčková ◽  
Z Dušek
Keyword(s):  
Phospholipase A2 ◽  
Elongation Factor ◽  
Normal Activity ◽  
Normal Function ◽  
Cholesterol Esterase ◽  
Elongation Factors ◽  
Ribosomal Subunits ◽  
Binding Factor ◽  
Peptide Elongation ◽  
Sepharose 4B

1. Peptide-elongation factors were purified from rat liver and treated with cholesterol esterase and phospholipase A2 immobilized on Sepharose 4B. 2. Binding of L-[3H]-phenylalanyl-tRNA to 40S ribosomal subunits was decreased by approx. 70% and to polyribosomes by 30% in the presence of the binding factor incubated with cholesterol esterase. Treatment of this factor with immobilized phospholipase A2 decreased the binding to smaller ribosomal subunits by only about 15%. 3. Poly(U)-dependent phenylalanine polymerization by ribosomal subunits was decreased to approx. 30% of its original value by treatment of both elongation factors with cholesterol esterase. 4. The normal activity of esterase-treated elongation factor in both the binding reaction and peptide-elongation assay was fully recovered by the addition of cholesteryl 14-methyl-hexadecanoate. 5. Different classes of lipids present in peptide-elongation factor 1 have apparently different functions. Whereas phospholipids are required to maintain the strcture of heavy aggregates of this factor, the presence of cholesteryl 14-methylhexadecanoate is obviously necessary for the normal function of peptide-elongation factors.

scholarly journals Influence of cholesteryl 14-methylhexadecanoate on some ribosomal functions required for peptide elongation

1974 ◽  
Vol 138 (2) ◽  
pp. 147-154 ◽  
Author(s):  
J. Hradec ◽  
Z. Dušek ◽  
O. Mach
Keyword(s):  
Ribosomal Subunit ◽  
Normal Activity ◽  
Peptidyl Transferase ◽  
Original Activity ◽  
Ribosomal Subunits ◽  
Freeze Dried ◽  
Peptide Elongation ◽  
Guanosine Triphosphatase ◽  
A Site ◽  
Chloroform Methanol

1. Polyribosomes and ribosomal subunits from rat liver were adsorbed on a cellulosic ion-exchange adsorbent, freeze-dried and extracted with organic solvents. The activity of extracted particles in peptide elongation was tested in the presence of purified peptideelongation factors. 2. Chloroform–methanol mixture (2:1, v/v) extracted 1.87±0.15 pmol of cholesteryl 14-methylhexadecanoate/pmol of the smaller ribosomal subunit and 0.92±0.11 pmol/pmol of the larger subunit. 3. In the presence of transferase I, extracted polyribosomes and 40S subunits bound more phenylalanyl-tRNA than did control non-extracted particles. The same binding as in control mixtures was obtained with extracted particles supplemented with cholesteryl 14-methylhexadecanoate in quantities corresponding to those extracted. 4. The polymerization of phenylalanine was greatly decreased with extracted polyribosomes and subunits and addition of the cholesteryl ester could not fully restore the original activity. 5. Extraction significantly decreased the activity of the P site of peptidyl transferase and normal activity was recovered after the addition of the ester. The A site of peptidyl transferase in extracted polyribosomes showed an increased activity when compared with non-extracted polyribosomes. 6. Cholesteryl 14-methylhexadecanoate apparently affects the function of the ribosomal A site and peptidyl transferase site and probably also that of the guanosine triphosphatase site and P site. The presence of different amounts of the ester in polyribosomes may be one of the mechanisms modulating peptide elongation at the ribosomal level.

scholarly journals Peptide elongation in rat kidney after cadmium administration

1980 ◽  
Vol 190 (3) ◽  
pp. 791-797 ◽  
Author(s):  
M J Kuliszewski ◽  
D M Nicholls
Keyword(s):  
Rat Kidney ◽  
Gel Filtration ◽  
Elongation Factor ◽  
Peptide Bond ◽  
Renal Tissue ◽  
Elongation Factors ◽  
Elongation Factor 2 ◽  
Peptide Elongation ◽  
Elongation Factor 1 ◽  
Trna Binding

Rats received two injections (each 2.6 mg/kg body wt.) of CdCl2, and the kidneys were removed 24 h later. Postmicrosomal supernatant fractions of the homogenized kidneys were used as a source of elongation factors 1 and 2 in assays for [14C]phenylalanyl-tRNA binding to ribosomes and for peptide-bond synthesis. After purification of these preparations by precipitation with (NH4)2SO4 and gel filtration on Sephadex G-200 and G-100, elongation factor 1 activity was significantly increased. A significant increase in the activity of purified elongation factor 2 was also found. The results are discussed in relation to the reported effects of CdCl2 and of HgCl2 on renal tissue.

scholarly journals The role of cholesteryl 14-methylhexadecanoate in peptide elongation reactions

1971 ◽  
Vol 123 (5) ◽  
pp. 959-966 ◽  
Author(s):  
J. Hradec ◽  
Z. Dušek ◽  
E. Bermek ◽  
H. Matthaei
Keyword(s):  
Cholesteryl Ester ◽  
Rat Liver ◽  
Enzyme Purification ◽  
Residual Activity ◽  
Normal Function ◽  
Enzymic Activity ◽  
Elongation Factors ◽  
Enzyme Preparations ◽  
Active Transfer ◽  
Peptide Elongation

1. Peptide-elongation factors were purified from rat liver and human tonsils and the contents of cholesteryl 14-methylhexadecanoate were determined in fractions obtained during enzyme purification. The relative contents of this compound in purified enzyme preparations was several times higher than that in the crude starting material. Elongation factors from human tonsils contained a significantly larger quantity of the cholesteryl ester than enzyme from rat liver. 2. Transfer enzymes extracted with various organic solvents showed variable decreased activities in both binding and peptidization assay. The decrease of enzymic activity was proportional to the amount of cholesteryl 14-methylhexadecanoate extracted from a given enzymic preparation. In systems containing both extracted elongation factors the polyphenylalanine synthesis was limited by the residual activity of the less active transfer factor. 3. The original enzymic activity of extracted transferases was fully recovered by the addition of pure cholesteryl 14-methylhexadecanoate in quantities corresponding to those extracted. 4. Increase of the relative contents of this cholesteryl ester during enzyme purification, decrease of the enzymic activity after the extraction and its recovery by the addition of this compound indicates that the presence of this ester in elongation factors is essential for the normal function of these enzymes.

scholarly journals CTP can replace GTP in reactions catalyzed by eukaryotic peptide elongation factor 1

FEBS Letters ◽  
1984 ◽  
Vol 177 (1) ◽  
pp. 112-114 ◽  
Author(s):  
Z. Tuháčková ◽  
M. Havránek ◽  
J. Hradec
Keyword(s):  
Elongation Factor ◽  
Peptide Elongation ◽  
Elongation Factor 1

scholarly journals The mode of action of Shiga toxin on peptide elongation of eukaryotic protein synthesis

1987 ◽  
Vol 244 (2) ◽  
pp. 287-294 ◽  
Author(s):  
T G Obrig ◽  
T P Moran ◽  
J E Brown
Keyword(s):  
Protein Synthesis ◽  
Complex Formation ◽  
Shiga Toxin ◽  
Mode Of Action ◽  
Elongation Factor ◽  
Shigella Dysenteriae ◽  
Gtpase Activity ◽  
Elongation Factor 2 ◽  
Peptide Elongation ◽  
Elongation Factor 1

The effect of Shiga toxin, from Shigella dysenteriae 1, on the component reactions of peptide elongation were investigated. Enzymic binding of [3H]phenylalanine-tRNA to reticulocyte ribosomes was inhibited by 50% at 7 nM toxin. Elongation factor 1 (eEF-1)-dependent GTPase activity was also inhibited. Both reactions were not restored by addition of excess eEF-1 protein. In contrast, toxin concentrations of 200 nM were required to inhibit by 50% the elongation factor 2 (eEF-2)-dependent translocation of aminoacyl-tRNA on ribosomes. Addition of excess eEF-2 restored translocation activity. The eEF-2-dependent GTPase activity was unaffected at toxin concentrations below 100 nM, and Shiga-toxin concentrations of up to 1,000 nM did not affect either GTP.eEF-2.ribosome complex-formation or peptidyltransferase activity. Thus Shiga toxin closely resembles alpha-sarcin in action, both being primary inhibitors of eEF-1-dependent reactions. In contrast, the 60 S ribosome inactivators ricin and phytolaccin are primary inhibitors of eEF-2-dependent reactions of peptide elongation.

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