BSU1 (At1g03445, UniProtKB:Q9LR78) curation notes

Session 2026-10-05/06 (brassinosteroid_signaling module curation).

• Identity checked: BSU1_ARATH, Q9LR78.
• Falcon deep research attempted; HTTP 402, no report.
• Kelch-repeat PPP Ser/Thr phosphatase, nuclear PMID:14977918.
• Key mechanism: dephosphorylates BIN2 pTyr200 PMID:19734888.
• Activated by CDG1 Ser764 phosphorylation PMID:21855796.
• NEW: GO:0004725 protein tyrosine phosphatase activity (IDA, PMID:19734888). Core function uses this term.
• IBA GO:0009966 too general -> MODIFY to GO:1900459.

2026-10-06 review follow-up (PR #4394)

• Direct BES1 dephosphorylation (Mora-Garcia 2004 interpretation) is not supported in vitro: PMID:19734888; PMID:19734888. Recorded as a DISPUTED finding_review on PMID:14977918; removed from description and core function 2.
• GO:0004722 kept: PMID:19734888.
• GO:0008138 (protein tyrosine/serine/threonine phosphatase activity) considered as a single replacement for the GO:0004722 + GO:0004725 pair; kept the pair because both activities are each directly evidenced and BSU1 is a PPP-fold (not DSP-fold) enzyme.