Bovine heart microsomes contain an Mr = 66,000 non-heme iron protein which stimulates NADPH oxidation

Bovine heart microsomes have been found to contain a non-heme iron protein which serves as an electron acceptor for NADPH-cytochrome P-450 reductase and therefore stimulates NADPH oxidation. This protein, tentatively referred to as Microsomal Iron Protein (MIP), has been extracted with Triton N-101...

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Bibliographic Details
Published in:The Journal of biological chemistry 1991-10, Vol.266 (30), p.20011-20017
Main Authors: MINOTTI, G, IKEDA-SAITO, M
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Cattle
Cell physiology
Chromatography, Liquid
Electrophoresis, Polyacrylamide Gel
Fundamental and applied biological sciences. Psychology
Metalloproteins - metabolism
Microsomes - metabolism
Molecular and cellular biology
Molecular Weight
Myocardium - metabolism
NADP - metabolism
Nonheme Iron Proteins
Oxidation-Reduction
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Summary:Bovine heart microsomes have been found to contain a non-heme iron protein which serves as an electron acceptor for NADPH-cytochrome P-450 reductase and therefore stimulates NADPH oxidation. This protein, tentatively referred to as Microsomal Iron Protein (MIP), has been extracted with Triton N-101 and purified by ion exchange chromatography on CM- and DEAE-celluloses and gel filtration on Sepharose 6B. MIP is an Mr = 66,000 monomer with 17 atoms of Fe(III)/molecule. Incubation with dithionite removes iron from MIP and abolishes the stimulation of NADPH oxidation, but subsequent incubation with nitrilotriacetic-Fe(III) reincorporates iron and restores the stimulation of NADPH oxidation. Oxygen is the ultimate electron acceptor. In the presence of oxygen, the enzymatic reduction of MIP Fe(III) is followed by the reoxidation of Fe(II) at the expense of oxygen, generating superoxide anion and regenerating MIP Fe(III) for the continuous oxidation of NADPH. In the absence of oxygen, electron transfer from the reductase to MIP Fe(III) causes the release of Fe(II), which limits the ability of MIP to serve as an electron acceptor and stimulate NADPH oxidation. The--NH2-terminal of MIP has been sequenced, and no homology has been found with the sequence of other iron storage or transport proteins such as ferritin or transferrin.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(18)54885-7