|3psg, resolution 1.65Å ()|
THE HIGH RESOLUTION CRYSTAL STRUCTURE OF PORCINE PEPSINOGEN
The structure of porcine pepsinogen at pH 6.1 has been refined to an R-factor of 0.173 for data extending to 1.65 A. The final model contains 180 solvent molecules and lacks density for residues 157-161. The structure of this aspartic proteinase zymogen possesses many of the characteristics of pepsin, the mature enzyme. The secondary structure of the zymogen consists predominantly of beta-sheet, with an approximate 2-fold axis of symmetry. The activation peptide packs into the active site cleft, and the N-terminus (1P-9P) occupies the position of the mature N-terminus (1-9). Thus changes upon activation include excision of the activation peptide and proper relocation of the mature N-terminus. The activation peptide or residues of the displaced mature N-terminus make specific interactions with the substrate binding subsites. The active site of pepsinogen is intact; thus the lack of activity of pepsinogen is not due to a deformation of the active site. Nine ion pairs in pepsinogen may be important in the advent of activation and involve the activation peptide or regions of the mature N-terminus which are relocated in the mature enzyme. The activation peptide-pepsin junction, 44P-1, is characterized by high thermal parameters and weak density, indicating a flexible structure which would be accessible to cleavage. Pepsinogen is an appropriate model for the structures of other zymogens in the aspartic proteinase family.
The high-resolution crystal structure of porcine pepsinogen., Hartsuck JA, Koelsch G, Remington SJ, Proteins. 1992 May;13(1):1-25. PMID:1594574
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
About this Structure
3psg is a 1 chain structure with sequence from Sus scrofa. This structure supersedes the now removed PDB entry 1psg. The December 2000 RCSB PDB Molecule of the Month feature on Pepsin by David S. Goodsell is 10.2210/rcsb_pdb/mom_2000_12. Full crystallographic information is available from OCA.