moaD

UniProt ID: Q88NB9
Organism: Pseudomonas putida (strain ATCC 47054 / DSM 6125 / CFBP 8728 / NCIMB 11950 / KT2440)
Review Status: DRAFT
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Gene Description

moaD encodes the small sulfur-carrier subunit of molybdopterin synthase. Its C-terminal glycine is adenylated by MoeB and converted to a thiocarboxylate; two sulfur-loaded MoaD molecules then donate the dithiolene sulfurs incorporated into cyclic pyranopterin monophosphate by the MoaD-MoaE synthase complex.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0006777 Mo-molybdopterin cofactor biosynthetic process
IEA
GO_REF:0000120 		ACCEPT
Summary: MoaD is the sulfur carrier required for molybdopterin formation.
Reason: UniProt family assignment, operon context with moaC/moaE, and the conserved MoaD carrier mechanism support this pathway annotation.
Supporting Evidence:
file:PSEPK/moaD/moaD-deep-research-openscientist.md
The gene **moaD** (UniProt **Q88NB9**; ordered locus **PP_1293**) of *Pseudomonas putida* strain KT2440 encodes the **small sulfur-carrier subunit of molybdopterin (MPT) synthase**, the enzyme that catalyzes the **second of the four conserved steps of molybdenum cofactor (Moco) biosynthesis**.
GO:1990133 molybdopterin adenylyltransferase complex
IEA
GO_REF:0000118 		ACCEPT
Summary: MoaD participates in the transient MoeB-MoaD adenylyltransferase complex during carrier activation.
Reason: MoeB-family proteins form a 2:2 complex with MoaD while adenylating its C-terminal glycine.
Supporting Evidence:
file:PSEPK/moeB/moeB-uniprot.txt
CC -!- SUBUNIT: Homodimer. Forms a stable heterotetrameric complex of 2 MoeB CC and 2 MoaD during adenylation of MoaD. {ECO:0000256|ARBA:ARBA00063809}.
GO:0097163 sulfur carrier activity
ISS
file:interpro/panther/PTHR33359/PTHR33359-entries.csv 		NEW
Summary: Q88NB9 is the molybdopterin-synthase sulfur carrier.
Reason: UniProt identifies Q88NB9 as the MoaD sulfur-carrier subunit, and the reviewed E. coli MoaD P30748 is in the same exact PANTHER subfamily. The carrier thiocarboxylate donates sulfur during molybdopterin synthesis.
Supporting Evidence:
file:PSEPK/moaD/moaD-uniprot.txt
DE RecName: Full=Molybdopterin synthase sulfur carrier subunit {ECO:0000256|ARBA:ARBA00024247};
file:PSEPK/moaD/moaD-uniprot.txt
DR PANTHER; PTHR33359:SF1; MOLYBDOPTERIN SYNTHASE SULFUR CARRIER SUBUNIT; 1.
file:interpro/panther/PTHR33359/PTHR33359-entries.csv
P30748,Molybdopterin synthase sulfur carrier subunit,protein,83333,Escherichia coli (strain K12),Escherichia coli (strain K12),moaD,81,PTHR33359:SF1,MOLYBDOPTERIN SYNTHASE SULFUR CARRIER SUBUNIT,True
GO:1990140 molybdopterin synthase complex
ISS
file:interpro/panther/PTHR33359/PTHR33359-entries.csv 		NEW
Summary: Q88NB9 is proposed as a component of the MoaD-MoaE molybdopterin synthase complex.
Reason: Q88NB9 and Escherichia coli MoaD P30748 occupy the same PTHR33359:SF1 sulfur-carrier subfamily, and Q88NB9 is encoded directly beside its MoaE partner. The conserved MoaD-MoaE heterotetramer therefore supports GO:1990140 by sequence similarity rather than direct KT2440 complex measurement.
Supporting Evidence:
file:PSEPK/moaE/moaE-uniprot.txt
CC -!- SUBUNIT: Heterotetramer of 2 MoaD subunits and 2 MoaE subunits. Also CC stable as homodimer. The enzyme changes between these two forms during CC catalysis. {ECO:0000256|ARBA:ARBA00026066}.
file:PSEPK/moaD/moaD-deep-research-openscientist.md
Mechanistically, MoaD operates within a **MoaD₂–MoaE₂ heterotetramer**. Each MoaD subunit inserts its reactive C-terminus deep into a MoaE catalytic subunit, positioning the C-terminal Gly-thiocarboxylate adjacent to the substrate **cyclic pyranopterin monophosphate (cPMP / precursor Z)**.
file:interpro/panther/PTHR33359/PTHR33359-entries.csv
P30748,Molybdopterin synthase sulfur carrier subunit,protein,83333,Escherichia coli (strain K12),Escherichia coli (strain K12),moaD,81,PTHR33359:SF1,MOLYBDOPTERIN SYNTHASE SULFUR CARRIER SUBUNIT,True

Core Functions

Sulfur-carrier subunit whose thiocarboxylated C terminus supplies the two sulfurs incorporated into molybdopterin by the MoaD-MoaE synthase.

Molecular Function:
sulfur carrier activity
Directly Involved In:
Mo-molybdopterin cofactor biosynthetic process
In Complex:
molybdopterin synthase complex
Supporting Evidence:
  • file:PSEPK/moaD/moaD-uniprot.txt
    DE RecName: Full=Molybdopterin synthase sulfur carrier subunit {ECO:0000256|ARBA:ARBA00024247};
  • file:PSEPK/moaD/moaD-deep-research-openscientist.md
    Mechanistically, MoaD operates within a **MoaD₂–MoaE₂ heterotetramer**. Each MoaD subunit inserts its reactive C-terminus deep into a MoaE catalytic subunit, positioning the C-terminal Gly-thiocarboxylate adjacent to the substrate **cyclic pyranopterin monophosphate (cPMP / precursor Z)**.

References

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Suggested Questions for Experts

Q: Which KT2440 sulfur-donor system converts adenylated MoaD to the active thiocarboxylate under physiological conditions?

Suggested Experiments

Experiment: Reconstitute Q88NB9 activation and thiocarboxylation with MoeB and candidate sulfur-donor proteins, then assay molybdopterin formation with MoaE.

Type: biochemical pathway reconstitution

Deep Research

OpenScientist

(moaD-deep-research-openscientist.md)

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