| Evidence type | Key finding | Quantitative data | Source (paper, year, URL) | Citation ID(s) |
|---|---|---|---|---|
| Domain/cluster homology | UniProt C5B1I5 corresponds to MexAM1_META1p4133 within the mll/mlu locus (META1p4129–4138); META1p4132–4135 are annotated as mllA, mllBC, mllDE, and mllF and are homologous to petrobactin asbABCDEF biosynthetic genes. The mllBC fusion is described as unusual among characterized homologs. antiSMASH detection for this locus used IucA_IucC, AMP-binding, PP-binding, and DUF6005 models, supporting assignment to an NRPS-independent siderophore-like pathway. | mll locus upregulated ~32-fold on average with Nd2O3 vs NdCl3 | Zytnick et al., 2022, https://doi.org/10.1101/2022.01.19.476857 | (pqac-00000008, pqac-00000009, pqac-00000014) |
| Transcriptomics | The methylolanthanin biosynthetic gene cluster was the most strongly induced gene set when cells were grown with poorly soluble lanthanide, consistent with a role in acquisition of low-bioavailability lanthanides. | ~32-fold average induction of mll locus with Nd2O3 vs NdCl3; related changes include xoxF1 ~5-fold, exaF ~3-fold, pqqA2/3 ~4-fold; M. extorquens senses lanthanides at ~2.5 nM | Zytnick et al., 2022, https://doi.org/10.1101/2022.01.19.476857 | (pqac-00000008, pqac-00000009, pqac-00000014) |
| Genetics | Cluster-level genetics link the locus containing META1p4133 to lanthanide physiology: deletion of mll reduces lanthanide bioaccumulation, while overexpression increases growth and Nd accumulation. Exogenous purified methylolanthanin rescues growth-related defects. | ΔmxaFΔmll shows ~30% lower lanthanide bioaccumulation in one assay; deletion caused 1.8-fold lower Nd bioaccumulation with NdCl3; overexpression increased Nd bioaccumulation ~3.5-fold on average; methylolanthanin added at 50 nM significantly increased growth yield (p = 0.036, 0.037) | Zytnick et al., 2022, https://doi.org/10.1101/2022.01.19.476857 | (pqac-00000011, pqac-00000012, pqac-00000014) |
| Metabolite structure | Deletion/overexpression of META1p4132–4138 established that the locus containing META1p4133 is required for production of methylolanthanin. Structural analysis showed a citrate core linked to two 4-hydroxybenzoate moieties via acetylated homospermidine residues, distinguishing it from rhodopetrobactin-like 3,4-DHB systems. | Diagnostic LC-MS features at m/z 799.4232 (positive) and 797.4092 (negative); related feature pair at m/z 721.4114/719.3978; n = 20 per group for peak-area statistics and n = 5 per group for volcano plots | Zytnick et al., 2022, https://doi.org/10.1101/2022.01.19.476857 | (pqac-00000003, pqac-00000010) |
| Metal-binding | Purified methylolanthanin directly binds lanthanides, supporting the interpretation that the META1p4133-containing biosynthetic cluster produces a lanthanophore/metallophore. Complexes were detected with multiple lanthanides. | Complex observed as [MLL-H++Ln3+]2+ with La, Nd, and Lu; cultures for metal-binding/growth assays used 2 µM NdCl3 or 1 µM Nd2O3 in reported experiments | Zytnick et al., 2022, https://doi.org/10.1101/2022.01.19.476857 | (pqac-00000004, pqac-00000006, pqac-00000011, pqac-00000012) |
| Localization/transport context | The locus includes predicted uptake and signaling components, indicating the product functions extracellularly/periplasmically in metal capture and import. META1p4129–4131 are predicted to encode a TonB-dependent outer membrane receptor, anti-sigma factor, and sigma factor; mllJ is predicted periplasmic. | Gene cluster spans META1p4129–4138 | Zytnick et al., 2022, https://doi.org/10.1101/2022.01.19.476857; Juma et al., 2022, https://doi.org/10.3389/fmicb.2022.921635 | (pqac-00000005, pqac-00000007, pqac-00000008, pqac-00000010) |
| Application/engineering | Engineering increased methylolanthanin/lanthanophore production to improve REE recovery from waste feedstocks. Expression of mll in trans increased uptake of multiple REEs from magnet swarf, supporting real-world bioleaching and bioaccumulation applications. | >3-fold increases in Nd, Pr, and Dy uptake; reached 80 mg Nd/g dry weight, 15 mg Pr/g dry weight, and 8 mg Dy/g dry weight; Nd yields >20-fold above baseline; estimated 1.3–2.1 g Nd/L and ~65–100% recovery in a single run with 1% Nd magnet swarf pulp density; scalable to 10 L | Good et al., 2023, https://doi.org/10.1021/acs.est.3c06775 | (pqac-00000013, pqac-00000018) |


*Table: This table summarizes the main lines of evidence supporting functional annotation of UniProt C5B1I5 (MexAM1_META1p4133; mllBC fusion) within the methylolanthanin biosynthetic locus of Methylorubrum extorquens AM1. It highlights what is directly supported by transcriptomic, genetic, structural, metal-binding, and engineering data, while distinguishing cluster-level inference from single-enzyme biochemical proof.*