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O93875 · ERG3_CANAX

  • Protein
    Delta(7)-sterol 5(6)-desaturase
  • Gene
    ERG3
  • Status
    UniProtKB reviewed (Swiss-Prot)
  • Amino acids
  • Protein existence
    Evidence at transcript level
  • Annotation score
    5/5

Function

function

C-5 sterol desaturase; part of the third module of ergosterol biosynthesis pathway that includes the late steps of the pathwa (PubMed:10433965, PubMed:20733039, PubMed:9000517).
ERG3 catalyzes the introduction of a C-5 double bond in the B ring to produce 5-dehydroepisterol (PubMed:10433965).
The third module or late pathway involves the ergosterol synthesis itself through consecutive reactions that mainly occur in the endoplasmic reticulum (ER) membrane. Firstly, the squalene synthase ERG9 catalyzes the condensation of 2 farnesyl pyrophosphate moieties to form squalene, which is the precursor of all steroids. Squalene synthase is crucial for balancing the incorporation of farnesyl diphosphate (FPP) into sterol and nonsterol isoprene synthesis. Secondly, the squalene epoxidase ERG1 catalyzes the stereospecific oxidation of squalene to (S)-2,3-epoxysqualene, which is considered to be a rate-limiting enzyme in steroid biosynthesis. Then, the lanosterol synthase ERG7 catalyzes the cyclization of (S)-2,3 oxidosqualene to lanosterol, a reaction that forms the sterol core. In the next steps, lanosterol is transformed to zymosterol through a complex process involving various demethylation, reduction and desaturation reactions. The lanosterol 14-alpha-demethylase ERG11 (also known as CYP51) catalyzes C14-demethylation of lanosterol to produce 4,4'-dimethyl cholesta-8,14,24-triene-3-beta-ol, which is critical for ergosterol biosynthesis. The C-14 reductase ERG24 reduces the C14=C15 double bond of 4,4-dimethyl-cholesta-8,14,24-trienol to produce 4,4-dimethyl-cholesta-8,24-dienol. 4,4-dimethyl-cholesta-8,24-dienol is substrate of the C-4 demethylation complex ERG25-ERG26-ERG27 in which ERG25 catalyzes the three-step monooxygenation required for the demethylation of 4,4-dimethyl and 4alpha-methylsterols, ERG26 catalyzes the oxidative decarboxylation that results in a reduction of the 3-beta-hydroxy group at the C-3 carbon to an oxo group, and ERG27 is responsible for the reduction of the keto group on the C-3. ERG28 has a role as a scaffold to help anchor ERG25, ERG26 and ERG27 to the endoplasmic reticulum and ERG29 regulates the activity of the iron-containing C4-methylsterol oxidase ERG25. Then, the sterol 24-C-methyltransferase ERG6 catalyzes the methyl transfer from S-adenosyl-methionine to the C-24 of zymosterol to form fecosterol. The C-8 sterol isomerase ERG2 catalyzes the reaction which results in unsaturation at C-7 in the B ring of sterols and thus converts fecosterol to episterol. The sterol-C5-desaturase ERG3 then catalyzes the introduction of a C-5 double bond in the B ring to produce 5-dehydroepisterol. The C-22 sterol desaturase ERG5 further converts 5-dehydroepisterol into ergosta-5,7,22,2428-tetraen-3beta-ol by forming the C-2223 double bond in the sterol side chain. Finally, ergosta-5,7,22,2428-tetraen-3beta-ol is substrate of the C-2428 sterol reductase ERG4 to produce ergosterol (Probable).

Miscellaneous

Defects in C-5 sterol desaturation results in antibiotic and azole resistance of Candida albicans during infection, particularly in AIDS patients.

Catalytic activity

Cofactor

Fe cation (UniProtKB | Rhea| CHEBI:24875 )

Pathway

Steroid metabolism; ergosterol biosynthesis; ergosterol from zymosterol: step 3/5.

GO annotations

AspectTerm
Cellular Componentendoplasmic reticulum lumen
Cellular Componentendoplasmic reticulum membrane
Molecular FunctionC-5 sterol desaturase activity
Molecular Functiondelta7-sterol 5(6)-desaturase activity
Molecular Functioniron ion binding
Biological Processergosterol biosynthetic process

Keywords

Enzyme and pathway databases

Names & Taxonomy

Protein names

  • Recommended name
    Delta(7)-sterol 5(6)-desaturase
  • EC number
  • Alternative names
    • C-5 sterol desaturase
    • Ergosterol Delta(5,6) desaturase
    • Ergosterol biosynthesis protein 3
    • Sterol-C5-desaturase

Gene names

    • Name
      ERG3

Organism names

  • Taxonomic identifier
  • Strain
    • ATCC 32354 / B311
  • Taxonomic lineage
    Eukaryota > Fungi > Dikarya > Ascomycota > Saccharomycotina > Saccharomycetes > Saccharomycetales > Debaryomycetaceae > Candida/Lodderomyces clade > Candida

Accessions

  • Primary accession
    O93875

Organism-specific databases

Subcellular Location

Features

Showing features for transmembrane.

TypeIDPosition(s)Description
Transmembrane120-140Helical
Transmembrane172-192Helical
Transmembrane206-226Helical
Transmembrane272-292Helical

Keywords

Phenotypes & Variants

Features

Showing features for natural variant.

TypeIDPosition(s)Description
Natural variant97in strain: azole-resistant isolates
Natural variant147in strain: azole-resistant isolates
Natural variant193in strain: azole-resistant isolates
Natural variant237in strain: azole-resistant isolates
Natural variant243in strain: azole-resistant isolates
Natural variant330in strain: azole-resistant isolates
Natural variant353in strain: azole-resistant isolates

Variants

We now provide the "Disease & Variants" viewer in its own tab.

The viewer provides 7 variants from UniProt as well as other sources including ClinVar and dbSNP.

Go to variant viewer

Chemistry

PTM/Processing

Features

Showing features for chain.

TypeIDPosition(s)Description
ChainPRO_00001170201-386Delta7-sterol 56-desaturase

Expression

Induction

Expression is repressed during spider biofilm formation.

Interaction

Family & Domains

Features

Showing features for domain, motif.

Type
IDPosition(s)Description
Domain214-337Fatty acid hydroxylase
Motif226-230Histidine box-1
Motif239-243Histidine box-2
Motif314-318Histidine box-3

Domain

The histidine box domains may contain the active site and/or be involved in metal ion binding.

Sequence similarities

Belongs to the sterol desaturase family.

Keywords

Family and domain databases

Sequence

  • Sequence status
    Complete
  • Length
    386
  • Mass (Da)
    45,447
  • Last updated
    1999-05-01 v1
  • MD5 Checksum
    BBC85BF91A89D4053F76E8DC60A2219A
MDIVLEICDYYLFDKVYADVFPKDGAVHEFLKPAIQSFSQIDFPSLPNLDSFDTNSTLISSNNFNISNVNPATIPSYLFSKIASYQDKSEIYGLAPKFFPATDFINTSFLARSNIFRETLSLFIITTIFGWLLYFIVAYLSYVFVFDKKIFNHPRYLKNQMSLEIKRATTAIPVMVLLTIPFFLLELNGYSFLYLDINECTGGYKAILWQIPKFILFTDCGIYFLHRWLHWPSVYKVLHKPHHKWIVCTPFASHAFHPVDGFFQSLPYHLYPLLFPLHKVLYLFLFTFVNFWTVMIHDGSYWSNDPVVNGTACHTVHHLYFNYNYGQFTTLWDRLGNSYRRPDDSLFVKDVKAEEEKKIWKEQTRKMEEIRGEVEGKVDDREYVEQ

Sequence databases

Nucleotide SequenceProtein SequenceMolecule TypeStatus
AF069752
EMBL· GenBank· DDBJ
AAC99343.1
EMBL· GenBank· DDBJ
Genomic DNA

Similar Proteins

Disclaimer

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