Journal: Nat Commun / Year: 2022 Title: Structure of the proteolytic enzyme PAPP-A with the endogenous inhibitor stanniocalcin-2 reveals its inhibitory mechanism. Authors: Sara Dam Kobberø / Michael Gajhede / Osman Asghar Mirza / Søren Kløverpris / Troels Rønn Kjær / Jakob Hauge Mikkelsen / Thomas Boesen / Claus Oxvig / Abstract: The metzincin metalloproteinase PAPP-A plays a key role in the regulation of insulin-like growth factor (IGF) signaling by specific cleavage of inhibitory IGF binding proteins (IGFBPs). Using single- ...The metzincin metalloproteinase PAPP-A plays a key role in the regulation of insulin-like growth factor (IGF) signaling by specific cleavage of inhibitory IGF binding proteins (IGFBPs). Using single-particle cryo-electron microscopy (cryo-EM), we here report the structure of PAPP-A in complex with its endogenous inhibitor, stanniocalcin-2 (STC2), neither of which have been reported before. The highest resolution (3.1 Å) was obtained for the STC2 subunit and the N-terminal approximately 1000 residues of the PAPP-A subunit. The 500 kDa 2:2 PAPP-A·STC2 complex is a flexible multidomain ensemble with numerous interdomain contacts. In particular, a specific disulfide bond between the subunits of STC2 and PAPP-A prevents dissociation, and interactions between STC2 and a module located in the very C-terminal end of the PAPP-A subunit prevent binding of its main substrate, IGFBP-4. While devoid of activity towards IGFBP-4, the active site cleft of the catalytic domain is accessible in the inhibited PAPP-A·STC2 complex, as shown by its ability to hydrolyze a synthetic peptide derived from IGFBP-4. Relevant to multiple human pathologies, this unusual mechanism of proteolytic inhibition may support the development of specific pharmaceutical agents, by which IGF signaling can be indirectly modulated.
Entire : Partial PAPP-A dimer in complex with subunit of its endogenous in...
Entire
Name: Partial PAPP-A dimer in complex with subunit of its endogenous inhibitor STC2 dimer
Components
Complex: Partial PAPP-A dimer in complex with subunit of its endogenous inhibitor STC2 dimer
Complex: PAPP-A
Complex: N-terminal part of PAPP-A
Protein or peptide: Pappalysin-1
Complex: C-terminal part of PAPP-A
Complex: Subunit of Stanniocalcin-2
Protein or peptide: Stanniocalcin-2
Ligand: 2-acetamido-2-deoxy-beta-D-glucopyranose
Ligand: ZINC ION
Ligand: CALCIUM ION
+
Supramolecule #1: Partial PAPP-A dimer in complex with subunit of its endogenous in...
Supramolecule
Name: Partial PAPP-A dimer in complex with subunit of its endogenous inhibitor STC2 dimer type: complex / ID: 1 / Parent: 0 / Macromolecule list: #1-#2 Details: Inhibited proteolytic complex generated by harvest of serum media, purifying on a nickel column followed by negative affinity purification and size-exclusion chromatography.
Source (natural)
Organism: Homo sapiens (human) / Tissue: ubiquitous / Location in cell: extracellular
Molecular weight
Theoretical: 500 KDa
+
Supramolecule #2: PAPP-A
Supramolecule
Name: PAPP-A / type: complex / ID: 2 / Parent: 1 / Macromolecule list: #1 / Details: Parts of both PAPP-A subunits
Source (natural)
Organism: Homo sapiens (human) / Tissue: ubiquitous / Location in cell: extracellular
+
Supramolecule #3: Subunit of Stanniocalcin-2
Supramolecule
Name: Subunit of Stanniocalcin-2 / type: complex / ID: 3 / Parent: 1 / Macromolecule list: #2 / Details: One subunit of the STC2 dimer
Source (natural)
Organism: Homo sapiens (human) / Tissue: ubiquitous / Location in cell: extracellular
+
Supramolecule #4: N-terminal part of PAPP-A
Supramolecule
Name: N-terminal part of PAPP-A / type: complex / ID: 4 / Parent: 2 / Macromolecule list: #1 Details: The first approximately 1000 residues of a PAPP-A subunit
Source (natural)
Organism: Homo sapiens (human) / Tissue: ubiquitous / Location in cell: extracellular
+
Supramolecule #5: C-terminal part of PAPP-A
Supramolecule
Name: C-terminal part of PAPP-A / type: complex / ID: 5 / Parent: 2 / Macromolecule list: #1 / Details: The C-terminal 240 residues of one PAPP-A subunit
Source (natural)
Organism: Homo sapiens (human) / Tissue: ubiquitous / Location in cell: extracellular
+
Macromolecule #1: Pappalysin-1
Macromolecule
Name: Pappalysin-1 / type: protein_or_peptide / ID: 1 / Number of copies: 2 / Enantiomer: LEVO / EC number: pappalysin-1
Source (natural)
Organism: Homo sapiens (human) / Cell: extracellular
Name: ZINC ION / type: ligand / ID: 4 / Number of copies: 1 / Formula: ZN
Molecular weight
Theoretical: 65.409 Da
+
Macromolecule #5: CALCIUM ION
Macromolecule
Name: CALCIUM ION / type: ligand / ID: 5 / Number of copies: 8 / Formula: CA
Molecular weight
Theoretical: 40.078 Da
-
Experimental details
-
Structure determination
Method
cryo EM
Processing
single particle reconstruction
Aggregation state
particle
-
Sample preparation
Concentration
0.6 mg/mL
Buffer
pH: 7.4 Component:
Concentration
Formula
Name
20.0 mM
Hepes
Hepes
100.0 mM
NaCl
NaCL
1.0 mM
CaCl
CaCl
Details: Hepes buffer, 20 mM Hepes pH 7.4 100 mM NaCl, 1 mM CaCl
Grid
Model: C-flat-2/2 / Material: COPPER / Mesh: 400 / Support film - Material: CARBON / Support film - topology: HOLEY / Pretreatment - Type: GLOW DISCHARGE / Pretreatment - Time: 45 sec.
Vitrification
Cryogen name: ETHANE / Chamber humidity: 90 % / Chamber temperature: 277.15 K / Instrument: LEICA EM GP / Details: 4 s.
-
Electron microscopy
Microscope
FEI TITAN KRIOS
Image recording
#0 - Image recording ID: 1 / #0 - Film or detector model: GATAN K3 BIOQUANTUM (6k x 4k) / #0 - Number grids imaged: 1 / #0 - Number real images: 32144 / #0 - Average exposure time: 0.91 sec. / #0 - Average electron dose: 59.0 e/Å2 / #1 - Image recording ID: 2 / #1 - Film or detector model: GATAN K3 BIOQUANTUM (6k x 4k) / #1 - Number grids imaged: 1 / #1 - Number real images: 10060 / #1 - Average exposure time: 0.8 sec. / #1 - Average electron dose: 58.0 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
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