Specificity of the induction of ferritin synthesis by hemin.
We have previously reported that hemin derepresses ferritin mRNA translation in vitro. As noted earlier, pre-incubation of a 90 kDa ferritin repressor protein (FRP) with hemin prevented subsequent repression of ferritin synthesis in a wheat germ extract. The significance of this observation has been investigated further. Evidence is presented here that this inactivation of FRP is temperature dependent. Neither FeCl3, Fe3+ chelated with EDTA, nor protoporphyrin IX caused significant inactivation of FRP under comparable conditions, whereas Zn2(+)-protoporphyrin IX produced an intermediate degree of inhibition. The presence of a glutathione redox buffer (GSB), which was previously shown to minimize non-specific side-effects of hemin, was not necessary for the derepression reaction. Inclusion of mannitol, a free radical scavenger, did not alter the inactivation caused by hemin. Calculation of the expected ratio of hemin monomers to dimers suggests that the active species is the monomer.
Lin
J J
JJ
Department of Biology, Washington University, St. Louis, MO 63130.
Daniels-McQueen
S
S
Gaffield
L
L
Patino
M M
MM
Walden
W E
WE
Thach
R E
RE
D000818:Animals; D016632:Apolipoprotein A-I; D001054:Apolipoproteins A / Q000235:genetics; D002352:Carrier Proteins / Q000378:metabolism*; D002712:Chlorides; D004262:DNA Restriction Enzymes / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D005290:Ferric Compounds / Q000494:pharmacology; D005293:Ferritins / Q000096:biosynthesis / Q000235:genetics*; D005296:Ferrous Compounds / Q000494:pharmacology; D006418:Heme / Q000494:pharmacology*; D006801:Humans; D035941:Iron Regulatory Protein 1; D035925:Iron-Regulatory Proteins; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000235:genetics; D014176:Protein Biosynthesis / Q000187:drug effects*; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism*; D013816:Thermodynamics
D016632:Apolipoprotein A-I; D001054:Apolipoproteins A; D002352:Carrier Proteins; D002712:Chlorides; D005290:Ferric Compounds; D005296:Ferrous Compounds; D035925:Iron-Regulatory Proteins; D008075:Lipoproteins, HDL; D012333:RNA, Messenger; C055526:Fe(II)-EDTA; D006418:Heme; D005293:Ferritins; D004492:Edetic Acid; D004262:DNA Restriction Enzymes; D035941:Iron Regulatory Protein 1; C024555:ferric chloride