1PCA

THREE DIMENSIONAL STRUCTURE OF PORCINE PANCREATIC PROCARBOXYPEPTIDASE A. A COMPARISON OF THE A AND B ZYMOGENS AND THEIR DETERMINANTS FOR INHIBITION AND ACTIVATION


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2 Å

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Three-dimensional structure of porcine pancreatic procarboxypeptidase A. A comparison of the A and B zymogens and their determinants for inhibition and activation.

Guasch, A.Coll, M.Aviles, F.X.Huber, R.

(1992) J.Mol.Biol. 224: 141-157


  • PubMed Abstract: 
  • The three-dimensional structure of procarboxypeptidase A (PCPA) from porcine pancreas has been determined at 2 A resolution and refined to a crystallographic R-factor of 0.198, with a root-mean-square deviation from ideal values for bond lengths of 0 ...

    The three-dimensional structure of procarboxypeptidase A (PCPA) from porcine pancreas has been determined at 2 A resolution and refined to a crystallographic R-factor of 0.198, with a root-mean-square deviation from ideal values for bond lengths of 0.015 A and for angles of 2.1 degrees. It is compared with procarboxypeptidase B (PCPB) from the same tissue. The 94/95 residue activation segments of PCPA/PCPB have equivalent folds: an N-terminal globular region with an open sandwich antiparallel alpha/antiparallel beta topology, followed by an extended alpha-helical segment, the connection to the enzyme. Alignment of the secondary structures of the activation segments of PCPA and PCPB (residues A1 to A99) indicates a two residue insertion between residues A34 and A35 and a C-terminal helix that is two turns longer in PCPA compared to PCPB. A deletion is observed between residues A43 to A45, the region containing the short 3(10) helix that covers the active site in PCPB. The globular region (A4 to A80) shields the preformed active center of carboxypeptidase A (CPA), but none of the residues involved in catalysis makes direct contacts with the activation segment. In contrast, subsites S2, S3 and S4 of the enzyme, involved in the binding of peptidic substrates, are blocked by specific contacts with residues AspA36, TrpA38, ArgA47, AspA53 and GluA86 of the activation segment. It has been described that several residues of CPA exhibit different conformations in the free enzyme compared to when substrate is bound: Arg127, Arg145, Glu270 and Tyr248. In PCPA all of these residues are found in the "active" conformation, as if substrate were actually bound. The presence of a ligand, tentatively interpreted as a free amino acid (Val) in the active center could explain this fact. The connecting region (A80 to A99), the target for proteolytic activation, establishes fewer contacts with the enzyme in PCPA than in PCPB. The activation segment of PCPA (A4 to A99) remains bound to the enzyme after the first trypsin cleavage between ArgA99-Ala1 probably due to the stability conferred on it by the alpha-helix (alpha 3) of the connecting segment. These and other structural features may explain the differences in intrinsic activity and different rates or proteolytic activation of each zymogen.


    Related Citations: 
    • Three-Dimensional Structure of Porcine Procarboxypeptidase B: A Structural Basis of its Inactivity
      Coll, M.,Guasch, A.,Aviles, F.X.,Huber, R.
      (1991) Embo J. 10: 1


    Organizational Affiliation

    Max-Planck-Institut für Biochemie, Martinsried bei München, Germany.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
PROCARBOXYPEPTIDASE A PCPA
A
403Sus scrofaGene Names: CPA1 (CPA)
EC: 3.4.17.1
Find proteins for P09954 (Sus scrofa)
Go to Gene View: CPA1
Go to UniProtKB:  P09954
Small Molecules
Ligands 3 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
ZN
Query on ZN

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Download CCD File 
A
ZINC ION
Zn
PTFCDOFLOPIGGS-UHFFFAOYSA-N
 Ligand Interaction
CIT
Query on CIT

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Download CCD File 
A
CITRIC ACID
C6 H8 O7
KRKNYBCHXYNGOX-UHFFFAOYSA-N
 Ligand Interaction
VAL
Query on VAL

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Download CCD File 
A
VALINE
C5 H11 N O2
KZSNJWFQEVHDMF-BYPYZUCNSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2 Å
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 127.060α = 90.00
b = 76.920β = 90.00
c = 47.520γ = 90.00
Software Package:
Software NamePurpose
EREFrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 1993-10-31
    Type: Initial release
  • Version 1.1: 2008-03-27
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance