Annotation inferences using phylogenetic trees
Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara
Combined Automated Annotation using Multiple IEA Methods
Hhat is a palmitoylacyltransferase with specificity for N-palmitoylation of Sonic Hedgehog.
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Purified Hhat attaches palmitate to the N-terminal cysteine of Shh through an amide (N-linked) bond, not a thioester.
"We provide direct biochemical evidence that Hhat is a PAT with specificity for attaching palmitate via amide linkage to the N-terminal cysteine of Shh."
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Hhat is selective for Hedgehog: PSD95 and Wnt are not substrates, and Porcupine does not palmitoylate Shh.
"Other palmitoylated proteins (e.g. PSD95 and Wnt) are not substrates for Hhat, and Porcupine, a putative Wnt PAT, does not palmitoylate Shh."
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Both the Shh precursor and the mature protein are N-palmitoylated, and the reaction occurs as Shh transits the secretory pathway.
"Both the Shh precursor and mature protein are N-palmitoylated by Hhat, and the reaction occurs during passage through the secretory pathway."
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Shh palmitoylation is required for effective short- and long-range signalling.
"Palmitoylation of Sonic Hedgehog (Shh) is critical for effective long- and short-range signaling."
Topological analysis of Hedgehog acyltransferase, a multipalmitoylated transmembrane protein.
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HHAT has ten transmembrane domains and two reentrant loops, with the catalytic His and Asp on opposite faces of the ER membrane.
"We show that HHAT is comprised of ten transmembrane domains and two reentrant loops with the critical His and Asp residues on opposite sides of the endoplasmic reticulum membrane."
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Mutating the conserved catalytic histidine abolishes HHAT palmitoylation activity.
"mutation of the conserved His residue in the hypothesized catalytic domain results in a complete loss of HHAT palmitoylation"
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HHAT is the ER enzyme that palmitoylates Hedgehog proteins, and is itself palmitoylated on multiple cytosolic cysteines.
"Hedgehog acyltransferase (HHAT) is the enzyme in the endoplasmic reticulum that palmitoylates Hedgehog proteins"
Hedgehog Acyltransferase Promotes Uptake of Palmitoyl-CoA across the Endoplasmic Reticulum Membrane.
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Shh palmitoylation is catalysed on the luminal side of the ER membrane by Hhat, an ER-resident enzyme, and the modification is essential for Shh signalling.
"Shh palmitoylation is catalyzed on the luminal side of the endoplasmic reticulum (ER) by Hedgehog acyltransferase (Hhat), an ER-resident enzyme. ... Attachment of palmitate to the N terminus of Sonic hedgehog (Shh) is essential for Shh signaling."
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Palmitoyl-CoA uptake across the ER membrane is an intrinsic property of Hhat, separable from its acyltransferase activity, so the enzyme also acts as a conduit for its own acyl donor.
"Reconstitution of purified Hhat into liposomes provided further evidence that palmitoyl-CoA uptake activity is an intrinsic property of Hhat. ... implying that Hhat serves a dual function as a palmitoyl acyltransferase and a conduit to supply palmitoyl-CoA to the luminal side of the ER."
A reference map of the human binary protein interactome.
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HuRI is a systematic yeast two-hybrid screen of the human ORFeome; the authors state that the cellular function of most of the interactions it reports is unknown.
"We screened this search space a total of nine times with a panel of three Y2H assay versions ... the cellular function of most individual PPIs remains to be elucidated"
Substrate and product complexes reveal mechanisms of Hedgehog acylation by HHAT.
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HHAT is an ER membrane protein that transfers palmitate from palmitoyl-CoA to the N-terminal cysteine of Hedgehog precursors, and Hedgehog precursors must undergo this modification before they can signal.
"HHAT is an endoplasmic reticulum (ER) membrane protein that catalyzes the transfer of a palmitoyl lipid from palmitoyl-CoA to the N-terminal cysteine of Hedgehog precursor proteins ... Before they can function as signaling molecules, Hedgehog precursor proteins must undergo amino-terminal palmitoylation by Hedgehog acyltransferase (HHAT)."
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The product complex resolves density for the amide linkage to the Hedgehog N-terminal cysteine C24, confirming that the transferred palmitate is N-linked.
"including density for the amide linkage to the N-terminal cysteine (C24) of Hedgehog, indicates that the palmitoylation reaction has occurred"
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HHAT brings together palmitoyl-CoA from the cytosolic side and the Hedgehog peptide from the ER lumen within a membrane-embedded active site.
"The structures reveal how HHAT overcomes the challenges of bringing together substrates that have different physiochemical properties from opposite sides of the endoplasmic reticulum membrane within a membrane-embedded active site for catalysis."
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The palmitate HHAT installs is required for downstream signalling and is structurally recognised by the Hedgehog receptor Patched1; Hedgehog proteins are thought to be HHAT's only substrates.
"The attached lipid is required for downstream signaling and is structurally recognized by the Hedgehog receptor Patched1 ... The enzyme displays exquisite selectivity for Hedgehog proteins, which are thought to be its only substrates"
Structure, mechanism, and inhibition of Hedgehog acyltransferase.
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Transfer of palmitate to the SHH N terminus by the multi-pass transmembrane enzyme HHAT is a key step in Hedgehog signalling.
"A key step in signaling is transfer of a palmitate group to the SHH N terminus, catalyzed by the multi-pass transmembrane enzyme Hedgehog acyltransferase (HHAT)."
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A heme group bound to HHAT is essential for its function.
"revealing a heme group bound to HHAT that is essential for HHAT function"
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HHAT adapts the membrane environment to move an acyl chain across the ER membrane, and the inhibitor IMP-1575 works by occluding the substrate site.
"Our multidisciplinary analysis provides a detailed view of the mechanism by which HHAT adapts the membrane environment to transfer an acyl chain across the endoplasmic reticulum membrane. ... A structure of HHAT bound to potent small-molecule inhibitor IMP-1575 revealed conformational changes in the active site that occlude substrate binding."
HHAT palmitoylates Hh N-terminal fragment
HHAT G287V doesn't palmitoylate Hh-Np