title: Regulation of protein synthesis in rabbit reticulocyte lysates by the heme-regulated protein kinase: inhibition of interaction of Met-tRNAfMet binding factor with another initiation factor in formation of Met-tRNAfMet.40S ribosomal subunit complexes.
abstract: Protein synthesis in reticulocytes and their lysates is regulated by heme. In heme deficiency a heme-regulated translational inhibitor (HRI) that blocks initiation of polypeptide chains is activated. HRI is a protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) that specifically phosphorylates the 38,000-dalton subunit of the Met-tRNA(f) (Met) binding factor (IF), which forms a ternary complex with Met-tRNA(f) (Met) and GTP, a finding that suggests that the inhibition by HRI involves the phosphorylation of IF. We have investigated the effect of HRI in the partial reactions of protein chain initiation in which the IF-promoted binding of Met-tRNA(f) (Met) to 40S ribosomal subunits is enhanced by another initiation factor [ternary complex dissociation factor (TDF)] and AUG. The results show that HRI at very low concentrations markedly inhibits the binding of Met-tRNA(f) (Met) to 40S subunits. The inhibitory effect of HRI requires ATP. Under these conditions HRI phosphorylates only the 38,000-dalton subunit of IF. The TDF preparations not only promote the binding of the ternary complex to 40S subunits but also promote the dissociation of the ternary complex in the presence of 5 mM Mg(2+) at 0 degrees . The preincubation of purified IF alone with low concentrations of HRI and ATP does not significantly affect its capacity to form the ternary complex; however, the TDF-promoted dissociation of the ternary complex is inhibited. The nonhydrolyzable analog adenosine 5'-[beta,gamma-imido]triphosphate does not substitute for ATP. These findings suggest that phosphorylation causes a conformational modification in IF, which results in inhibition of the interaction between the ternary complex and TDF that is required for the binding of the ternary complex to 40S subunits.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D006418:Heme / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D008715:Methionine; D010442:Peptide Chain Initiation, Translational; D010448:Peptide Initiation Factors / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism; D014176:Protein Biosynthesis; D011494:Protein Kinases / Q000378:metabolism*; D012343:RNA, Transfer / Q000378:metabolism*; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D010448:Peptide Initiation Factors; D010710:Phosphates; D006418:Heme; D000255:Adenosine Triphosphate; D012343:RNA, Transfer; D008715:Methionine; D011494:Protein Kinases; D008274:Magnesium
references.citation: Biochem Biophys Res Commun. 1965 Jan 18;18:236-42
references.pmid: 14282023
references.citation: Proc Natl Acad Sci U S A. 1976 Oct;73(10):3506-10
references.pmid: 1068462
references.citation: Proc Natl Acad Sci U S A. 1976 Sep;73(9):3112-6
references.pmid: 184460
references.citation: FEBS Lett. 1977 Apr 1;76(1):1-10
references.pmid: 323054
references.citation: Biochem Biophys Res Commun. 1977 Sep 9;78(1):161-9
references.pmid: 907668
references.citation: Proc Natl Acad Sci U S A. 1977 Aug;74(8):3326-9
references.pmid: 198782
references.citation: Proc Natl Acad Sci U S A. 1977 Apr;74(4):1445-9
references.pmid: 193100
references.citation: Proc Natl Acad Sci U S A. 1977 Jun;74(6):2264-8
references.pmid: 196285
references.citation: Proc Natl Acad Sci U S A. 1976 Sep;73(9):3078-82
references.pmid: 184458
references.citation: Nature. 1976 Sep 9;263(5573):163-5
references.pmid: 184395
references.citation: Cell. 1977 May;11(1):187-200
references.pmid: 559547
references.citation: Biochem Biophys Res Commun. 1977 Oct 24;78(4):1433-41
references.pmid: 921787
references.citation: Biochem Biophys Res Commun. 1977 Jan 24;74(2):559-69
references.pmid: 836310
references.citation: Proc Natl Acad Sci U S A. 1976 Dec;73(12):4349-53
references.pmid: 1069987
references.citation: Biochem Biophys Res Commun. 1976 Dec 6;73(3):625-31
references.pmid: 1008879
references.citation: J Biol Chem. 1976 Oct 25;251(20):6379-87
references.pmid: 977577
references.citation: Biochem Biophys Res Commun. 1976 Aug 23;71(4):1234-41
references.pmid: 971309
references.citation: J Mol Biol. 1972 May 28;66(3):471-81
references.pmid: 5037023
references.citation: Nat New Biol. 1973 Mar 14;242(115):35-8
references.pmid: 4512006
references.citation: Biochim Biophys Acta. 1973 Oct 26;324(3):397-409
references.pmid: 4762417
references.citation: Biochim Biophys Acta. 1970 Jul 16;213(1):237-40
references.pmid: 5488930
references.citation: Proc Natl Acad Sci U S A. 1974 Aug;71(8):2946-50
references.pmid: 4528641
references.citation: Proc Natl Acad Sci U S A. 1966 Mar;55(3):650-5
references.pmid: 5221248
references.citation: Proc Natl Acad Sci U S A. 1968 Feb;59(2):582-9
references.pmid: 5238986
references.citation: Cold Spring Harb Symp Quant Biol. 1969;34:567-78
references.pmid: 5266178
references.citation: Proc Natl Acad Sci U S A. 1973 Jan;70(1):41-5
references.pmid: 4509663
references.citation: J Mol Biol. 1973 May 25;76(3):379-403
references.pmid: 4732074
references.citation: Nat New Biol. 1973 Jan 31;241(109):150-2
references.pmid: 4512619
references.citation: Proc Natl Acad Sci U S A. 1975 Oct;72(10):3947-51
references.pmid: 1105571
references.citation: Biochem Biophys Res Commun. 1972 Jul 11;48(1):1-9
references.pmid: 4557509
references.citation: Biochim Biophys Acta. 1972 Nov 16;287(1):124-33
references.pmid: 4652795
references.citation: Nature. 1975 Oct 16;257(5527):616-8
references.pmid: 1101076
references.citation: Proc Natl Acad Sci U S A. 1976 Aug;73(8):2720-4
references.pmid: 1066685
references.citation: Eur J Biochem. 1976 JUL 1;66(2):413-22
references.pmid: 947756
references.citation: J Biol Chem. 1975 Dec 10;250(23):9067-75
references.pmid: 1194277
references.citation: Biochem Biophys Res Commun. 1975 Nov 17;67(2):689-95
references.pmid: 1201048
references.citation: Arch Biochem Biophys. 1968 May;125(2):671-83
references.pmid: 5656815