9hre
Peptide-substrate-binding (PSB) domain of human type I collagen prolyl 4-hydroxylase complexed with Pro-Hyp-Gly-Pro-Ala-Gly-Pro-Hyp-Gly.
Structural highlights
FunctionP4HA1_HUMAN Catalyzes the post-translational formation of 4-hydroxyproline in -Xaa-Pro-Gly- sequences in collagens and other proteins. Publication Abstract from PubMedCollagen prolyl 4-hydroxylase (C-P4H) catalyzes the 4-hydroxylation of Y-prolines of the XYG-repeat of procollagen. C-P4Hs are tetrameric alpha(2)beta(2) enzymes. The alpha-subunit provides the N-terminal dimerization domain, the middle peptide-substrate-binding (PSB) domain, and the C-terminal catalytic (CAT) domain. There are three isoforms of the alpha-subunit, complexed with a beta-subunit that is protein disulfide isomerase, forming C-P4H I-III. The PSB domain of the alpha-subunit binds proline-rich peptides, but its function with respect to the prolyl hydroxylation mechanism is unknown. An extended mode of binding of proline-rich peptides (PPII, polyproline type-II, conformation) to the PSB-I domain has previously been reported for the PPG-PPG-PPG and P9 peptides. Crystal structures now show that peptides with the motif PxGP (PPG-PRG-PPG, PPG-PAG-PPG) (where x, at Y-position 5, is not a proline) bind to the PSB-I domain differently, more deeply, in the peptide-binding groove. The latter mode of binding has previously been reported for structures of the PSB-II domain complexed with these PxGP-peptides. In addition, it is shown here by crystallographic binding studies that the POG-PAG-POG peptide (with 4-hydroxyprolines at Y-positions 2 and 8) also adopts the PxGP mode of binding to PSB-I as well as to PSB-II. Calorimetric binding studies show that the affinities of these peptides are lower for PSB-I than for PSB-II, with, respectively, K(D) values of about 70 muM for PSB-I and 20 muM for PSB-II. The importance of these results for understanding the reaction mechanism of C-P4H, in particular concerning the function of the PSB domain, is discussed. Binding Differences of the Peptide-Substrate-Binding Domain of Collagen Prolyl 4-Hydroxylases I and II for Proline- and Hydroxyproline-Rich Peptides.,Rahman MM, Sulu R, Adediran B, Tu H, Salo AM, Murthy S, Myllyharju J, Wierenga RK, Koski MK Proteins. 2025 Oct;93(10):1732-1746. doi: 10.1002/prot.26839. Epub 2025 May 19. PMID:40386874[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
| ||||||||||||||||||||
