Gene Ontology annotation through association of InterPro records with GO terms

GO_REF:0000002 supplied one or more source GOA annotations reviewed in this file.

Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping

SwissProt keyword-derived (SPKW) annotations present in the Sept 2025 goa_uniprot_gcrp snapshot but removed from the current GOA release after GOA retired the keyword2GO pipeline for cellular organisms.

Manual transfer of experimentally-verified manual GO annotation data to orthologs by curator judgment of sequence similarity

GO_REF:0000024 supplied one or more source GOA annotations reviewed in this file.

GO_REF:0000033

Annotation inferences using phylogenetic trees

GO_REF:0000033 supplied one or more source GOA annotations reviewed in this file.

GO_REF:0000044

Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt

GO_REF:0000044 supplied one or more source GOA annotations reviewed in this file.

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods

GO_REF:0000120 supplied one or more source GOA annotations reviewed in this file.

file:POPTR/METK1/METK1-uniprot.txt

UniProtKB reviewed entry for METK1

UniProt identifies METK1 as methionine adenosyltransferase, catalyzing S-adenosyl-L-methionine formation from L-methionine, ATP, and water in the cytoplasm.

file:POPTR/METK1/METK1-goa.tsv

QuickGO GOA annotations for METK1

GOA rows supplied the existing_annotations reviewed in this file.

file:POPTR/METK1/METK1-deep-research-falcon.md

Falcon deep-research report on METK1 (Populus trichocarpa S-adenosylmethionine synthase 1, UniProt A9P822)

METK1/SAMS/MAT (EC 2.5.1.6) catalyzes formation of S-adenosyl-L-methionine (SAM/AdoMet) from L-methionine and ATP via an SN2-type reaction in which the methionine sulfur attacks the 5' carbon of the ATP ribose; the report confirms this is the most defensible high-confidence enzyme-function annotation for A9P822.
The catalytic mechanism requires Mg2+ and K+ cofactors that coordinate the substrates, corroborating the metal ion binding (cofactor) requirement of the enzyme.
SAM produced by METK1 is the universal activated methyl donor for methyltransferases acting on DNA, histones, RNA, proteins and small molecules, and is a branch-point precursor feeding ethylene and polyamine biosynthesis - placing METK1 as a central one-carbon/methyl-transfer metabolic capacity enzyme rather than a pathway-specific regulator.
Plant SAMS is reported to localize to the cytoplasm and nucleus, with SAM synthesized in the cytoplasm and distributed to organelles by dedicated SAM transporters; this supports the cytosolic localization annotation for METK1.
In poplar (Populus x euramericana) exposed to SO2, metK/SAMS is up-regulated together with ACS in a resistant cultivar, providing direct genus-level evidence that METK1-type SAM-synthesis capacity participates in stress-associated metabolic remodeling; no primary study assays the specific P. trichocarpa A9P822 protein, so functional annotation rests on orthology/family inference.