SlyD review notes

2026-08-30 refresh and evidence collection

Refreshed UniProt and GOA through just fetch-gene ECOLI SlyD --force. The current
GOA has 35 physical rows but 32 unique term/evidence/reference signatures because
several protein binding records differ only by WITH/FROM partner. Three prior
records are absent from current GOA: GO:0016853, GO:0046872, and GO:0051082.
Falcon deep research timed out after 600 seconds and the configured Perplexity-lite
fallback failed for quota. The existing Falcon report was retained unchanged and
the review instead uses the 21 cached publications plus this manual journal.
All 21 cited PMIDs were successfully checked by just fetch-gene-pmids ECOLI SlyD.
Most caches are abstract-only; experimental annotations are therefore reviewed with
curator deference rather than removed when assay details cannot be reconstructed.
just fetch-fitness ECOLI SlyD could not reach a local FEBA source or the remote
endpoint. The corrected wrapper exited nonzero and wrote no fitness artifact, so no
phenotype inference is made from missing data.

The N-terminal FKBP domain is a bona fide PPIase. The family study reports that
“All SlyD variants catalyze the proline-limited refolding of ribonuclease T1” and
that SlyD has pronounced chaperone properties PMID:16388577. The PAINT slice for
PTHR47861 places GO:0003755, GO:0042026, and cytosol at PTN005358675; SlyD itself
is one of the experimental descendants supporting those ancestral assertions.
This self appearance is expected IBA evidence, not circularity.
SlyD is also a nickel metallochaperone for [NiFe]-hydrogenase maturation. Loss of
slyD reduces nickel accumulation and hydrogenase processing, while excess nickel
rescues the phenotypes [PMID:15569666, “These experiments demonstrate that SlyD
has a role in the nickel insertion step of the hydrogenase maturation pathway”].
SlyD stimulates nickel release from HypB [PMID:17426034, “SlyD stimulates release
of nickel from the high affinity Ni(II)-binding site of HypB”] and contacts HycE
before metal insertion [PMID:21185288, “A SlyD-HycE interaction preceding both
iron and nickel insertion to the enzyme was detected”]. GO:0170061 is therefore
an evidence-matched authored term.
Nickel maturation is separable from PPIase catalysis: PPIase-deficient mutants do
not show corresponding hydrogenase-production defects [PMID:17720786, “Mutations
that result in deficient PPIase activity do not produce corresponding decreases
in the other activities of SlyD in vitro or in hydrogenase production levels in
vivo”].

The insert-in-flap domain directly recognizes unfolded or partially folded clients
and slows insulin aggregation [PMID:19356587, “NMR titration experiments revealed
that the IF domain recognizes and binds unfolded or partially folded proteins and
peptides. Insulin aggregation is markedly slowed by SlyD*”]. This is a constitutive,
ATP-independent in-situ holdase activity.
GO:0051082 is now obsolete and has disappeared from the current SlyD GOA. It should
not remain as an authored core-function ID. GO:0140309 is also not evidence-matched:
its definition requires escort to an acceptor molecule or defined location, whereas
the SlyD anti-aggregation experiments demonstrate binding and stabilization in situ,
not a delivery step. The project-standard general holdase chaperone activity NTR
is retained as the ontology request [file:projects/UNFOLDED_PROTEIN_BINDING.md].