Gene Ontology annotation through association of InterPro records with GO terms
Manual transfer of experimentally-verified manual GO annotation data to orthologs by curator judgment of sequence similarity
Annotation inferences using phylogenetic trees
Combined Automated Annotation using Multiple IEA Methods
UniProtKB entry P52062 (HEMW_ECOLI)
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UniProt curates HemW as a probable heme chaperone for NarI that binds one heme per monomer, has no coproporphyrinogen III dehydrogenase activity, is cytoplasmic, and dimerizes when the cluster is bound.
"Probably acts as a heme chaperone, transferring heme to the NarI subunit of the respiratory enzyme nitrate reductase"
The radical SAM protein HemW is a heme chaperone.
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E. coli HemW binds one heme per subunit, needs an intact [4Fe-4S] cluster for dimerization and heme transfer but not for heme binding, interacts with bacterioferritins and NarI, and transfers bound heme to heme-depleted nitrate reductase, restoring its activity.
"heme that was covalently bound to HemW was actively transferred to a heme-depleted, catalytically inactive nitrate reductase"
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Full text (PMC5818191): E. coli hemW fails to complement the anaerobic growth defect of a hemN deletion strain, so HemW lacks coproporphyrinogen III dehydrogenase activity. HemW binds [14C]SAM but cleaves it only at a background rate. SAM did not affect heme transfer. A hemW mutant shows a slight, reproducible growth defect under nitrate respiration.
Lactococcus lactis HemW (HemN) is a haem-binding protein with a putative role in haem trafficking.
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L. lactis HemW, the ISS donor, lacks coproporphyrinogen III dehydrogenase activity in vivo and in vitro, contains an Fe-S cluster, binds heme b covalently (one per monomer), and has cytosolic and membrane-associated forms. HemW-like proteins form a distinct clade.
"showed that it is devoid of CPDH activity in vivo and in vitro"
Radical SAM Enzymes Involved in Tetrapyrrole Biosynthesis and Insertion.
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Review: HemW is the cytoplasmic heme chaperone that inserts heme b into NarGHI; the cluster is needed for transfer; the radical SAM mechanism of transfer is unresolved.
"heme is inserted into enzymes by the cytoplasmic heme chaperone HemW"