Variobactin and variochelin photoreactive lipopeptide siderophore biosynthesis and transport

A conserved hybrid polyketide synthase / nonribosomal peptide synthetase (PKS/NRPS) biosynthetic and iron-transport module (the var gene cluster) in soil and rhizosphere Variovorax species (exemplified by Variovorax paradoxus P4B GenBank KT362218 producing variobactin A/B, and Variovorax boronicumulans and Variovorax sp. H002 producing variochelins A-E). Downstream of the unreviewed starter NRPS Var3 (ALG65336.1, loading the N-acyl-arginine starter unit), the cytoplasmic hybrid PKS/NRPS/TauD megasynthase Var4 (VarG) extends the N-acyl-arginine starter with a malonate/methylmalonate ketide unit, reduces the beta-keto group, condenses the ketide-extended intermediate with the position-3 aspartate monomer loaded in trans on Var5 (ALG65340.1), and beta-hydroxylates that aspartate residue via its C-terminal TauD domain to install the photoreactive beta-hydroxyaspartate (Hya; reported as L-erythro-Hya for TauD-type hydroxylases in PMID:38590537, though L-threo-Hya was earlier reported for variochelin A in PMID:27023373) ligand; the bimodular NRPS Var6 elongates and epimerizes two internal peptide monomers (established as D-Ser and L-Pro in Variovorax sp. H002 variochelins in PMID:38590537, with Ser/Thr combinatorialization and amino-acid substitutions noted in V. paradoxus P4B variobactin A/B in PMID:26412281); and the terminal bimodular NRPS-thioesterase Var7 incorporates two C-terminal modified N-hydroxyornithine hydroxamate chelators (established as N-delta-acetyl-N-delta-hydroxy-L-ornithine in H002 variochelins and combinatorialized across N-formyl/N-acetyl/unmodified N-hydroxyornithine in P4B variobactin) and cleaves the mature lipopeptide siderophore. The inner-membrane SyrD-family type I ABC half-transporter Var14 exports the apo-siderophore across the cytoplasmic membrane. After extracellular Fe(III) chelation (and optional light-driven Fe(III)-to-Fe(II) photolysis), the outer-membrane TonB-dependent receptor Var8 imports ferric-variobactin/variochelin across the outer membrane, and following uptake into the cytoplasm, the FhuF-family ferric-siderophore reductase Var13 reduces complexed Fe(III) to release bioavailable Fe(II).

MODULE:variochelin_siderophore_biosynthesis_and_uptakeDRAFTMetabolic Pathwaymodules/variochelin_siderophore_biosynthesis_and_uptake.yaml
siderophore biosynthetic processGO:0019290 siderophore-iron import into cellGO:0033214
GO:0019290
siderophore biosynthetic process
GO:0019290 provides the biological-process context for assembly of the photoreactive lipopeptide siderophores variobactin and variochelin.
GO:0033214
siderophore-iron import into cell
GO:0033214 provides the biological-process context for TonB-dependent ferric-siderophore uptake and intracellular reductive iron release.
PMID:26412281
An automated Genomes-to-Natural Products platform (GNP) for the discovery of modular natural products.
Identifies the Variovorax paradoxus P4B var hybrid NRPS/PKS gene cluster (GenBank KT362218) and isolates and structurally characterizes its lipopeptide siderophore products variobactin A and B.
A second Variovorax isolate (V. paradoxus P4B (ref. 32)) was found to possess another distinct NRPS/PKS gene cluster, corresponding to a putative lipopeptide (Fig. 2b, Supplementary Fig. 17a and Supplementary Table 7). By altering amino-acid composition, macrocyclization status and tailoring modifications, we generated a library of 32 structures (Supplementary Fig. 17b) for use in GNP analysis of the LC–MS/MS spectrum. The crude extract of V. paradoxus P4B was shown to contain a series of candidate hits (Fig. 2b) whose isolation yielded the novel natural products variobactin A and B, in spite of several unforeseen amino-acid substitutions
PMID:26412281
An automated Genomes-to-Natural Products platform (GNP) for the discovery of modular natural products.
Describes the GNP combinatorialization of position-3 beta-hydroxyaspartate, interchangeable Ser/Thr, malonate/methylmalonate, and N-formylated, N-acetylated, or unmodified N-hydroxyornithine monomers for the V. paradoxus P4B var cluster.
The prediction was modified as the presence of an aspartate β-hydroxylating enzyme led to the conclusion that the predicted position 3 aspartate was β-hydroxyaspartate. This structure was combinatorialized to generate the linear lipopeptide and lipodepsipeptide macrocycle forms, with serines and threonines being interchangeable, the polyketide portion incorporating either a malonate or methylmalonate, and predicted N-hydroxyornithines being N-formylated, N-acetylated or not further modified, yielding a concentrated library of 32 hypothetical structures.
PMID:27023373
Variochelins, Lipopeptide Siderophores from Variovorax boronicumulans Discovered by Genome Mining.
Characterizes the orthologous Variovorax var PKS/NRPS gene cluster and demonstrates that the ferric complexes of its lipopeptide siderophores are photoreactive.
In this paper, we describe the genomics-driven discovery and characterization of variochelins, lipopeptide siderophores from the bacterium Variovorax boronicumulans, which thrives in soil and freshwater habitats. Variochelins are different from most other lipopeptide siderophores in that their biosynthesis involves a polyketide synthase. We demonstrate that the ferric iron complex of variochelin A possesses photoreactive properties and present the MS-derived structures of two degradation products that emerge upon light exposure.
PMID:38590537
New variochelins from soil-isolated Variovorax sp. H002.
Demonstrates by targeted varG::cmR gene replacement that the hybrid PKS/TauD module is essential for variochelin A-E biosynthesis and that its embedded TauD domain installs the photoreactive beta-hydroxyaspartate moiety.
To investigate whether the identified var biosynthetic gene cluster is responsible for variochelin production, we substituted varG encoding the polyketide synthase (PKS) module with a chloramphenicol resistance (cmR) gene cassette, using homologous recombination (Figure 3b). As a result, the varG knock-out mutant no longer produced 1–5, validating that the var biosynthetic gene cluster is indispensable for variochelin production in Variovorax sp. H002 (Figure 3b).
file:VARPD/var4/var4-ai-review.yaml
Variovorax paradoxus var4 gene review
A0A0N7FMV9 (ALG65339.1) encodes the hybrid PKS/NRPS and embedded TauD beta-aspartyl dioxygenase module Var4.
file:VARPD/var4/var4-bioinformatics/RESULTS.md
Sequence, Topology, and GenBank KT362218.1 Cluster Audit of Var4 (UniProtKB:A0A0N7FMV9)
Documents all 14 CDSs (var1-var14) of GenBank KT362218.1 (41,899 bp), including the non-monotonic GenBank protein_id assignment across var1 (ALG65337.1), var2 (ALG65338.1), and var3 (ALG65336.1) followed in locus order by var4-var14 (ALG65339.1-ALG65349.1), and confirms that Var4 lacks an embedded PF00501 adenylation domain.
GenBank `KT362218.1` (`41,899 bp`) contains 14 CDSs (`var1`–`var14`) with non-monotonic `protein_id` assignment across the first three ORFs (`var1` `1..834` = `ALG65337.1` thioesterase, `var2` `812..1513` = `ALG65338.1` phospantetheinyl transferase, `var3` `1510..6735` = `ALG65336.1` nonribosomal peptide synthetase) followed in locus order by `var4`–`var14` (`ALG65339.1`–`ALG65349.1`): var1 (1..834) = ALG65337.1 [thioesterase]; var2 (812..1513) = ALG65338.1 [phospantetheinyl transferase]; var3 (1510..6735) = ALG65336.1 [nonribosomal peptide synthetase]; var4 (6735..13772) = ALG65339.1 [polyketide synthase]; var5 (13769..16882) = ALG65340.1 [nonribosomal peptide synthetase]; var6 (16879..24630) = ALG65341.1 [nonribosomal peptide synthetase]; var7 (24670..31965) = ALG65342.1 [nonribosomal peptide synthetase]; var8 (complement(32061..34508)) = ALG65343.1 [TonB receptor]; var9 (complement(34707..35735)) = ALG65344.1 [fecr-like protein]; var10 (complement(35732..36310)) = ALG65345.1 [RNA polymerase subunit sigma-24]; var11 (complement(36472..37791)) = ALG65346.1 [lysine N-monooxygenase]; var12 (complement(37778..38884)) = ALG65347.1 [n-acetyltransferase]; var13 (complement(38953..39738)) = ALG65348.1 [ferric iron reductase]; var14 (40220..41899) = ALG65349.1 [cyclic peptide transporter].
file:VARPD/var6/var6-ai-review.yaml
Variovorax paradoxus var6 gene review
A0A0N9LX43 (ALG65341.1) encodes the bimodular NRPS elongation and epimerization subunit Var6.
file:VARPD/var7/var7-ai-review.yaml
Variovorax paradoxus var7 gene review
A0A0N9LYB5 (ALG65342.1) encodes the terminal bimodular NRPS and C-terminal chain-releasing thioesterase subunit Var7.
file:VARPD/var14/var14-ai-review.yaml
Variovorax paradoxus var14 gene review
A0A0N9LS79 (ALG65349.1) encodes the inner-membrane SyrD-family type I ABC siderophore exporter Var14.
file:VARPD/var8/var8-ai-review.yaml
Variovorax paradoxus var8 gene review
A0A0N9M610 (ALG65343.1) encodes the TonB-dependent outer-membrane ferric-variobactin receptor Var8.
file:VARPD/var13/var13-ai-review.yaml
Variovorax paradoxus var13 gene review
A0A0N9M354 (ALG65348.1) encodes the cytoplasmic FhuF-family ferric-siderophore reductase Var13.
7Nodes
6Parts
0Variant Sets
0Variants
9Annotons
5Connections

Derived QC

Recommended-field compliance

100.0% recommended fields populated

All recommended fields populated.

Module deep research

✗ none found

No MODULE:variochelin_siderophore_biosynthesis_and_uptake deep-research report alongside the module YAML.

Leaf nodes lacking representative members

✓ every leaf node grounds to a representative protein.

Template conformance

✓ every declared conforms_to bundle matches its template motif.

Function consistency and core coverage

9 gene-function check(s) reflected in core functions · 0 conflict(s) · 9 evidence or coverage gap(s) (18 comparison(s))

Retained noncore functions are reported separately; they do not require promotion to core functions. Support from representative genes does not establish conservation across the whole family. Missing reviews or identifiers leave a claim unverified.

AnnotonParticipantFunctionAssessment
var4_acyltransferase_activity var4 (Variovorax paradoxus P4B)
UniProtKB:A0A0N7FMV9
Family Representative 		polyketide synthase activity
GO:0016218 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
var4_nrps_condensation_activity var4 (Variovorax paradoxus P4B)
UniProtKB:A0A0N7FMV9
Family Representative 		non-ribosomal peptide synthetase activity
GO:1904091 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
var4_taud_dioxygenase_activity var4 (Variovorax paradoxus P4B)
UniProtKB:A0A0N7FMV9
Family Representative 		2-oxoglutarate-dependent dioxygenase activity
GO:0016706 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
var6_ligase_activity var6 (Variovorax paradoxus P4B)
UniProtKB:A0A0N9LX43
Family Representative 		non-ribosomal peptide synthetase activity
GO:1904091 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
var7_ligase_activity var7 (Variovorax paradoxus P4B)
UniProtKB:A0A0N9LYB5
Family Representative 		non-ribosomal peptide synthetase activity
GO:1904091 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
var7_thioesterase_activity var7 (Variovorax paradoxus P4B)
UniProtKB:A0A0N9LYB5
Family Representative 		thiolester hydrolase activity
GO:0016790 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
var14_abc_exporter_activity var14 (Variovorax paradoxus P4B)
UniProtKB:A0A0N9LS79
Family Representative 		ABC-type transporter activity
GO:0140359 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
var8_receptor_transporter_activity var8 (Variovorax paradoxus P4B)
UniProtKB:A0A0N9M610
Family Representative 		siderophore uptake transmembrane transporter activity
GO:0015344 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
var13_reductase_activity var13 (Variovorax paradoxus P4B)
UniProtKB:A0A0N9M354
Family Representative 		ferric-chelate reductase activity
GO:0000293 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
var4_acyltransferase_activity Var4/VarG hybrid PKS/NRPS/TauD siderophore megasynthases
Family 		polyketide synthase activity
GO:0016218 		Family Id Missing
The family has no identifier linking it to a curated family review.
var4_nrps_condensation_activity Var4/VarG hybrid PKS/NRPS/TauD siderophore megasynthases
Family 		non-ribosomal peptide synthetase activity
GO:1904091 		Family Id Missing
The family has no identifier linking it to a curated family review.
var4_taud_dioxygenase_activity Var4/VarG hybrid PKS/NRPS/TauD siderophore megasynthases
Family 		2-oxoglutarate-dependent dioxygenase activity
GO:0016706 		Family Id Missing
The family has no identifier linking it to a curated family review.
var6_ligase_activity Var6 bimodular variobactin/variochelin NRPS elongases
Family 		non-ribosomal peptide synthetase activity
GO:1904091 		Family Id Missing
The family has no identifier linking it to a curated family review.
var7_ligase_activity Var7 terminal variobactin/variochelin NRPS-thioesterases
Family 		non-ribosomal peptide synthetase activity
GO:1904091 		Family Id Missing
The family has no identifier linking it to a curated family review.
var7_thioesterase_activity Var7 terminal variobactin/variochelin NRPS-thioesterases
Family 		thiolester hydrolase activity
GO:0016790 		Family Id Missing
The family has no identifier linking it to a curated family review.
var14_abc_exporter_activity Var14 SyrD-family lipopeptide siderophore ABC exporters
Family 		ABC-type transporter activity
GO:0140359 		Family Id Missing
The family has no identifier linking it to a curated family review.
var8_receptor_transporter_activity Var8 TonB-dependent ferric-variobactin/variochelin receptors
Family 		siderophore uptake transmembrane transporter activity
GO:0015344 		Family Id Missing
The family has no identifier linking it to a curated family review.
var13_reductase_activity Var13 FhuF-family ferric-siderophore reductases
Family 		ferric-chelate reductase activity
GO:0000293 		Family Id Missing
The family has no identifier linking it to a curated family review.

Gene-review completeness (6/6 grounded genes reviewed)

6 complete review(s) · 0 with deep research · 0 missing review · 6 reviewed but lacking deep research

Gene Review Complete Deep research
var13 A0A0N9M354 ✓ ✓ ✗
var14 A0A0N9LS79 ✓ ✓ ✗
var4 A0A0N7FMV9 ✓ ✓ ✗
var6 A0A0N9LX43 ✓ ✓ ✗
var7 A0A0N9LYB5 ✓ ✓ ✗
var8 A0A0N9M610 ✓ ✓ ✗

Details

Variobactin and variochelin photoreactive lipopeptide siderophore biosynthesis and transportMetabolic Pathwayvariochelin_siderophore_biosynthesis_and_uptake
siderophore biosynthetic processGO:0019290 siderophore-iron import into cellGO:0033214

Grounded on the six GOA-annotated proteins of the Variovorax paradoxus strain P4B (NCBITaxon:34073) variobactin gene cluster (GenBank KT362218.1, 41,899 bp, var1-var14; PMID:26412281) — A0A0N7FMV9 (Var4, ALG65339.1), A0A0N9LX43 (Var6, ALG65341.1), A0A0N9LYB5 (Var7, ALG65342.1), A0A0N9M610 (Var8, ALG65343.1), A0A0N9M354 (Var13, ALG65348.1), and A0A0N9LS79 (Var14, ALG65349.1) — together with comparative characterization and varG::cmR knockout validation of the orthologous variochelin var gene clusters in Variovorax boronicumulans (PMID:27023373) and Variovorax sp. H002 (PMID:38590537). Note that GenBank KT362218.1 assigns protein_id accessions non-monotonically across the first three ORFs (verified in var4-bioinformatics/KT362218_features.gb and RESULTS.md), followed in locus order by var4-var14 (ALG65339.1-ALG65349.1). Remaining ORFs in GenBank KT362218.1 lacking UniProt GOA records account for the upstream starter and intervening assembly-line steps: var1 (1..834, ALG65337.1, GenBank note "thioesterase", type II editing thioesterase), var2 (812..1513, ALG65338.1, GenBank note "phospantetheinyl transferase", 4'-phosphopantetheinyl transferase), var3 (1510..6735, ALG65336.1, GenBank note "nonribosomal peptide synthetase", starter NRPS loading the N-terminal fatty-acyl and L-arginine units upstream of Var4), var5 (13769..16882, ALG65340.1, GenBank note "nonribosomal peptide synthetase", intervening NRPS module between var4 and var6 that activates and tethers the position-3 aspartate monomer in trans for Var4's LCL condensation and TauD beta-hydroxylase domains), var9/var10 (complement(34707..35735) / complement(35732..36310), ALG65344.1/ALG65345.1, FecR-like anti-sigma factor and ECF sigma-24 subunit paired with Var8's STN domain), and var11/var12 (complement(36472..37791) / complement(37778..38884), ALG65346.1/ALG65347.1, GenBank notes "lysine N-monooxygenase" and "n-acetyltransferase", supplying the N-hydroxylated and N-acylated ornithine substrates of Var7). Similarly, the inner-membrane transporter mediating periplasm-to-cytoplasm import of ferric-variobactin between outer-membrane Var8 and cytoplasmic Var13 is uncharacterized and recorded as KNOWLEDGE_GAP.

Connections

Var4 condenses the polyketide-extended starter chain onto the position-3 aspartate monomer tethered in trans on Var5 (ALG65340.1) and beta-hydroxylates it via its TauD domain before handoff from Var5 to the first NRPS module of Var6.
Var6 elongates and epimerizes the two internal peptide monomers (established as D-Ser and L-Pro in Variovorax sp. H002 variochelins) and passes the lipotetrapeptidyl chain to the terminal NRPS-thioesterase Var7.
Thioesterase offloading by Var7 releases mature apo-variobactin in the cytoplasm for export across the inner membrane by Var14.
Secreted variobactin chelates environmental Fe(III) extracellularly to form ferric-variobactin, the substrate imported across the outer membrane by Var8.
Following outer-membrane translocation by Var8 and inner-membrane uptake into the cytoplasm, ferric-variobactin is reduced by Var13 to liberate Fe(II).
Part 1: polyketide ketide elongation and TauD-catalyzed beta-aspartyl hydroxylation of the lipopeptidyl intermediate
Var4 hybrid PKS elongation and TauD beta-aspartyl hydroxylationReactionvar4_pks_taud_step

Annotons

Var4 hybrid PKS/NRPS ketide elongation module
var4_acyltransferase_activity
Participant: Family: Var4/VarG hybrid PKS/NRPS/TauD siderophore megasynthases
Family:
Var4/VarG hybrid PKS/NRPS/TauD siderophore megasynthases
Representative Members: var4 (Variovorax paradoxus P4B)UniProtKB:A0A0N7FMV9

Function

polyketide synthase activityGO:0016218
Substrates: methylmalonyl-CoA
Products: 4-acylamino-7-guanidino-3-hydroxy-2-methylheptanoyl-S-ACP

Incorporates a malonate or methylmalonate polyketide unit onto the N-acyl-arginine starter unit (loaded upstream on Var3 / ALG65336.1) and reduces the beta-keto group via its KS-AT-KR-ACP module.

Var4 LCL-type NRPS condensation domain
var4_nrps_condensation_activity
Participant: Family: Var4/VarG hybrid PKS/NRPS/TauD siderophore megasynthases
Family:
Var4/VarG hybrid PKS/NRPS/TauD siderophore megasynthases
Representative Members: var4 (Variovorax paradoxus P4B)UniProtKB:A0A0N7FMV9

Function

non-ribosomal peptide synthetase activityGO:1904091
Substrates: 4-acylamino-7-guanidino-3-hydroxy-2-methylheptanoyl-S-ACP L-aspartyl-S-PCP
Products: L-aspartyl-containing lipodipeptidyl-S-PCP

Condenses the polyketide-extended 4-acylamino-7-guanidino-3-hydroxy-2-methylheptanoyl-S-ACP intermediate with the position-3 aspartate monomer loaded in trans on Var5 (ALG65340.1) to form the Var5-tethered lipodipeptidyl-S-PCP intermediate (note that whether TauD beta-hydroxylation occurs after or prior to LCL condensation on Var5-tethered Asp remains experimentally open).

Var4 embedded TauD-family beta-aspartyl dioxygenase domain
var4_taud_dioxygenase_activity
Participant: Family: Var4/VarG hybrid PKS/NRPS/TauD siderophore megasynthases
Family:
Var4/VarG hybrid PKS/NRPS/TauD siderophore megasynthases
Representative Members: var4 (Variovorax paradoxus P4B)UniProtKB:A0A0N7FMV9

Function

2-oxoglutarate-dependent dioxygenase activityGO:0016706
Substrates: L-aspartyl-containing lipodipeptidyl-S-PCP 2-oxoglutarate dioxygen
Products: beta-hydroxyaspartyl-containing lipodipeptidyl-S-PCP succinate CO2

Catalyzes Fe(II)/2-oxoglutarate-dependent beta-hydroxylation of the Var5-tethered position-3 aspartate residue (modeled sequentially on L-aspartyl-containing lipodipeptidyl-S-PCP, though hydroxylation of L-aspartyl-S-PCP prior to LCL condensation is also mechanistically plausible) to install the photoreactive beta-hydroxyaspartate iron-coordinating ligand.

Part 2: bimodular NRPS activation, condensation, and epimerization of two internal peptide monomers (established as D-Ser and L-Pro in Variovorax sp. H002 variochelins; Ser/Thr combinatorialization and substitutions noted in P4B variobactin)
Var6 bimodular NRPS peptide elongation and epimerizationReactionvar6_nrps_elongation_step

Annotons

Var6 bimodular nonribosomal peptide synthetase
var6_ligase_activity
Participant: Family: Var6 bimodular variobactin/variochelin NRPS elongases
Family:
Var6 bimodular variobactin/variochelin NRPS elongases
Representative Members: var6 (Variovorax paradoxus P4B)UniProtKB:A0A0N9LX43

Function

non-ribosomal peptide synthetase activityGO:1904091
Substrates: L-alpha-amino acid ATP
Products: lipotetrapeptidyl-S-PCP

Activates, condenses, and epimerizes two internal peptide monomers (established as L-Ser epimerized to D-Ser and L-Pro in Variovorax sp. H002 variochelins, PMID:38590537, with Ser/Thr interchange and amino-acid substitutions noted in V. paradoxus P4B variobactin A/B, PMID:26412281) onto the growing lipopeptidyl-S-PCP intermediate.

Part 3: incorporation of two C-terminal modified N-hydroxyornithine hydroxamate chelators and thioesterase offloading of mature variobactin
Var7 terminal NRPS elongation and thioesterase chain releaseReactionvar7_nrps_release_step

Annotons

Var7 terminal bimodular NRPS subunit
var7_ligase_activity
Participant: Family: Var7 terminal variobactin/variochelin NRPS-thioesterases
Family:
Var7 terminal variobactin/variochelin NRPS-thioesterases
Representative Members: var7 (Variovorax paradoxus P4B)UniProtKB:A0A0N9LYB5

Function

non-ribosomal peptide synthetase activityGO:1904091
Substrates: N-hydroxyornithine derivative ATP
Products: variobactinyl-S-PCP

Activates and condenses the two C-terminal modified N-hydroxyornithine residues (established as N-delta-acetyl-N-delta-hydroxy-L-ornithine in H002 variochelins, PMID:38590537, and combinatorialized across N-formylated, N-acetylated, or unmodified N-hydroxyornithine in P4B variobactin, PMID:26412281) that form the bidentate hydroxamate iron-binding ligands.

Var7 C-terminal offloading thioesterase domain
var7_thioesterase_activity
Participant: Family: Var7 terminal variobactin/variochelin NRPS-thioesterases
Family:
Var7 terminal variobactin/variochelin NRPS-thioesterases
Representative Members: var7 (Variovorax paradoxus P4B)UniProtKB:A0A0N9LYB5

Function

thiolester hydrolase activityGO:0016790
Substrates: variobactinyl-S-PCP
Products: variobactin

Hydrolyzes the full-length lipohexapeptidyl-S-PCP thioester to release the mature apo-siderophore variobactin into the cytoplasm.

Part 4: ATP-coupled inner-membrane export of apo-variobactin
Var14 ABC transporter-mediated siderophore exportTransport Stepvar14_siderophore_export_step

Annotons

Var14 SyrD-family type I ABC siderophore exporter
var14_abc_exporter_activity
Participant: Family: Var14 SyrD-family lipopeptide siderophore ABC exporters
Family:
Var14 SyrD-family lipopeptide siderophore ABC exporters
Representative Members: var14 (Variovorax paradoxus P4B)UniProtKB:A0A0N9LS79

Function

ABC-type transporter activityGO:0140359
Substrates: variobactin ATP
Products: extracellular variobactin ADP

Couples ATP hydrolysis to the export of newly synthesized apo-variobactin across the cytoplasmic membrane.

Part 5: TonB-energized outer-membrane import of ferric-variobactin
Var8 TonB-dependent outer-membrane ferric-siderophore importTransport Stepvar8_outer_membrane_import_step

Annotons

Var8 TonB-dependent outer-membrane ferric-variobactin receptor
var8_receptor_transporter_activity
Participant: Family: Var8 TonB-dependent ferric-variobactin/variochelin receptors
Family:
Var8 TonB-dependent ferric-variobactin/variochelin receptors
Representative Members: var8 (Variovorax paradoxus P4B)UniProtKB:A0A0N9M610

Function

siderophore uptake transmembrane transporter activityGO:0015344
Substrates: ferric-variobactin
Products: periplasmic ferric-variobactin

Recognizes extracellular ferric-variobactin complexes and mediates TonB-dependent import across the bacterial cell outer membrane.

Part 6: cytoplasmic reductive release of ferrous iron from imported ferric-variobactin
Var13 FhuF-family ferric-siderophore reductionReactionvar13_ferric_reductase_step

Annotons

Var13 FhuF-family ferric-siderophore reductase
var13_reductase_activity
Participant: Family: Var13 FhuF-family ferric-siderophore reductases
Family:
Var13 FhuF-family ferric-siderophore reductases
Representative Members: var13 (Variovorax paradoxus P4B)UniProtKB:A0A0N9M354

Function

ferric-chelate reductase activityGO:0000293
Substrates: ferric-variobactin
Products: Fe(II) variobactin

Catalyzes one-electron reduction of Fe(III) bound to imported variobactin, releasing bioavailable Fe(II) for cellular incorporation.