title: The peptide-substrate-binding domain of human collagen prolyl 4-hydroxylases. Backbone assignments, secondary structure, and binding of proline-rich peptides.
abstract: The collagen prolyl 4-hydroxylases (C-P4Hs) catalyze the formation of 4-hydroxyproline by the hydroxylation of proline residues in -Xaa-Pro-Gly-sequences. The vertebrate enzymes are alpha 2 beta 2 tetramers in which protein-disulfide isomerase serves as the beta subunit. Two isoforms of the catalytic alpha subunit have been identified and shown to form [alpha(I)]2 beta 2 and [alpha(II)]2 beta 2 tetramers, the type I and type II C-P4Hs, respectively. The peptide-substrate-binding domain of type I C-P4H has been shown to be located between residues 138 and 244 in the 517-residue alpha(I) subunit and to be distinct from the catalytic domain that is located in the C-terminal region. We report here that a recombinant human C-P4H alpha(I) polypeptide Phe144-Ser244 forms a folded domain consisting of five alpha helices and one short beta strand. This structure is quite different from those of other proline-rich peptide-binding modules, which consist mainly of beta strands. Binding of the peptide (Pro-Pro-Gly)2 to this domain caused major chemical shifts in many backbone amide resonances, the residues showing the largest shifts being mainly hydrophobic, including three tyrosines. The Kd values determined by surface plasmon resonance and isothermal titration calorimetry for the binding of several synthetic peptides to the alpha(I) and the corresponding alpha(II) domain were very similar to the Km and Ki values for these peptides as substrates and inhibitors of the type I and type II C-P4H tetramers. The Kd values of the alpha(I) and alpha(II) domains for (Gly-Pro-4Hyp)5 were much higher than those for (Pro-Pro-Gly)5, indicating a marked decrease in the affinity of hydroxylated peptides for the domain. Many characteristic features of the binding of peptides to the type I and type II C-P4H tetramers can thus be explained by the properties of binding to this domain rather than the catalytic domain.
authors.affiliation: Collagen Research Unit, Biocenter Oulu and Department of Medical Biochemistry and Molecular Biology, University of Oulu, FIN-90014 Oulu, Finland.
authors.forename: Reija
authors.initials: R
authors.lastname: Hieta
authors.forename: Liisa
authors.initials: L
authors.lastname: Kukkola
authors.forename: Perttu
authors.initials: P
authors.lastname: Permi
authors.forename: Päivi
authors.initials: P
authors.lastname: Pirilä
authors.forename: Kari I
authors.initials: KI
authors.lastname: Kivirikko
authors.forename: Ilkka
authors.initials: I
authors.lastname: Kilpeläinen
authors.forename: Johanna
authors.initials: J
authors.lastname: Myllyharju
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002942:Circular Dichroism; D003094:Collagen / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D011393:Procollagen-Proline Dioxygenase / Q000737:chemistry* / Q000378:metabolism*; D011392:Proline; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D010455:Peptides; D021122:Protein Subunits; D011994:Recombinant Proteins; D003094:Collagen; D011392:Proline; D011393:Procollagen-Proline Dioxygenase