L. Catasus et al., THE SEQUENCE AND CONFORMATION OF HUMAN PANCREATIC PROCARBOXYPEPTIDASEA2 - CDNA CLONING, SEQUENCE-ANALYSIS, AND 3-DIMENSIONAL MODEL, The Journal of biological chemistry, 270(12), 1995, pp. 6651-6657
A full-length cDNA clone coding for human pancreatic preprocarboxypept
idase A2 has been isolated from a lambda gt11 human pancreatic library
, Expression clones were identified by specific interaction with antis
era raised against the native protein. The open reading frame of the p
olynucleotide sequence is 1254 base pairs in length and encodes a prot
ein of 417 amino acids, This cDNA includes a short leader signal pepti
de of 16 amino acids and a 94-amino acid-long activation segment, The
amino acid sequence shows 89% identity to that of rat procarboxypeptid
ase A2, the only A2 form sequenced so far, and 64% identity to that of
human procarboxypeptidase A1. The newly determined sequence was model
ed to the three-dimensional crystal structures of both bovine carboxyp
eptidase A and porcine procarboxypeptidase A1 by a novel distance geom
etry approach, Biases in the modeling were avoided by relying exclusiv
ely on automatic procedures and by using random structures as starting
points, Information taken from the known homologous structures refers
only to the backbone since no explicit data describing the conformati
on of side chains were transferred, Ten structures of human carboxypep
tidase A2 were determined on the basis of each of the two known crysta
l structures, The root-mean-square distance for the backbone atoms bet
ween the 10 structures and their mean for 237 selected residues is 0.7
Angstrom when starting from the bovine protein and 0.8 Angstrom for 2
51 selected residues when starting from the porcine protein. The 94 re
sidue-long activation segment was also determined in the modeling base
d on the porcine zymogen; its structure is well defined but not its or
ientation with respect to the enzyme moiety. The model obtained for hu
man procarboxypeptidase A2 is discussed with respect to the specificit
y and activation of the enzyme.