Carrier domain-containing protein (mllDE, locus MexAM1_META1p4134) belonging to the methylolanthanin (mll) biosynthetic gene cluster (META1p4129-META1p4138) of Methylorubrum extorquens AM1. UniProt assigns this 436-residue protein a PROSITE CARRIER domain (PS50075) together with a phosphopantetheine-binding/ACP-like fold (Pfam PF00550 PP-binding; IPR009081) and a DUF6005 domain (Pfam PF19468). The mll cluster is homologous in part to the petrobactin asbABCDEF NRPS-independent siderophore locus and is required to synthesize methylolanthanin, a secreted lanthanide-binding metallophore ("lanthanophore") rather than an iron siderophore. By homology to AsbD, the phosphopantetheine-binding/ACP-like carrier role places mllDE within the core biosynthetic machinery, although no source has biochemically characterized mllDE in isolation; functional assignment is therefore based on domain content plus cluster-level (homology, deletion/overexpression, and ~32-fold lanthanide-induced expression) evidence. The locus is strongly upregulated in response to poorly soluble lanthanides.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0031177 phosphopantetheine binding | NAS | NEW | Summary: Reviewer-proposed molecular function. UniProt assigns this protein a CARRIER domain (PROSITE PS50075) and a PP-binding/ACP-like fold (Pfam PF00550, IPR009081), and the falcon deep research independently infers a carrier/PP-binding ACP-like role for the mll cluster by homology to the petrobactin AsbD acyl carrier protein. Phosphopantetheine binding is the best-supported core molecular function for the ACP-like carrier domain. Reason: Best-supported molecular function from the UniProt carrier/PP-binding domain content, corroborated by homology-based inference in the deep research. Holds the 4'-phosphopantetheine prosthetic group needed for carrier function in lanthanophore assembly. Supporting Evidence: file:METEA/mllDE/mllDE-deep-research-falcon.md an inferred **carrier/PP-binding ACP-like role somewhere within the core mll biosynthetic machinery |
| GO:0044550 secondary metabolite biosynthetic process | NAS | NEW | Summary: Reviewer-proposed biological process. mllDE is a member of the methylolanthanin (mll) biosynthetic gene cluster, whose deletion and overexpression alter production of methylolanthanin, a secreted lanthanide-binding metallophore. Methylolanthanin is a small-molecule secondary metabolite. GO has no "metallophore biosynthetic process" term, and "siderophore biosynthetic process" (GO:0019290) would incorrectly imply iron specificity, so this general secondary metabolite biosynthesis term is the most accurate biological-process placement. Reason: Captures the pathway-level role of mllDE in biosynthesis of the methylolanthanin lanthanophore (a secondary metabolite), supported by cluster membership and deletion/overexpression phenotypes in the deep research. Deliberately avoids GO:0019290 (siderophore) because methylolanthanin is a lanthanide chelator, not an iron siderophore. Supporting Evidence: file:METEA/mllDE/mllDE-deep-research-falcon.md the most defensible functional statement is that **mllDE encodes a component of the methylolanthanin biosynthetic machinery**, likely contributing to assembly/modification steps required to produce the final lanthanophore |
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