Purification of a novel flavoprotein involved in the thyroid NADPH oxidase. Cloning of the porcine and human cdnas

Hydrogen peroxide is the final electron acceptor for the biosynthesis of thyroid hormone catalyzed by thyroperoxidase at the apical surface of thyrocytes. Pig and human thyroid plasma membrane contain a Ca(2+)-dependent NAD(P)H oxidase that generates H(2)O(2) by transferring electrons from NAD(P)H t...

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Bibliographic Details
Published in:The Journal of biological chemistry 1999-12, Vol.274 (52), p.37265-37269
Main Authors: Dupuy, C, Ohayon, R, Valent, A, Noël-Hudson, M S, Dème, D, Virion, A
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Arsenicals - metabolism
chromosome 15
Chromosome Mapping
Cloning, Molecular
Flavoproteins - chemistry
Flavoproteins - genetics
Flavoproteins - isolation & purification
Humans
In Situ Hybridization, Fluorescence
Molecular Sequence Data
Mox protein
NADPH oxidase
NADPH Oxidases - chemistry
NADPH Oxidases - genetics
NADPH Oxidases - isolation & purification
Phox protein
rbohA protein
RNA, Messenger - analysis
Swine
Thyroid Gland - enzymology
Tox protein
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Summary:Hydrogen peroxide is the final electron acceptor for the biosynthesis of thyroid hormone catalyzed by thyroperoxidase at the apical surface of thyrocytes. Pig and human thyroid plasma membrane contain a Ca(2+)-dependent NAD(P)H oxidase that generates H(2)O(2) by transferring electrons from NAD(P)H to molecular oxygen. We purified from pig thyroid plasma membrane a flavoprotein which constitutes the main, if not the sole, component of the thyroid NAD(P)H oxidase. Microsequences permitted the cloning of porcine and human full-length cDNAs encoding, respectively, 1207- and 1210-amino acid proteins with a predicted molecular mass of 138 kDa (p138(Tox)). Human and porcine p138(Tox) have 86.7% identity. The strongest similarity was to a predicted polypeptide encoded by a Caenorhabditis cDNA and with rbohA, a protein involved in the Arabidopsis NADPH oxidase. p138(Tox) shows also similarity to the p65(Mox) and to the gp91(Phox) in their C-terminal region and have consensus sequences for FAD- and NADPH-binding sites. Compared with gp91(Phox), p138(Tox) shows an extended N-terminal containing two EF-hand motifs that may account for its calcium-dependent activity, whereas three of four sequences implicated in the interaction of gp91(Phox) with the p47(Phox) cytosolic factor are absent in p138(Tox). The expression of porcine p138(Tox) mRNA analyzed by Northern blot is specific of thyroid tissue and induced by cyclic AMP showing that p138(Tox) is a differentiation marker of thyrocytes. The gene of human p138(Tox) has been localized on chromosome 15q15.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.274.52.37265