title: Metal Stabilization of Collagen and de Novo Designed Mimetic Peptides.
abstract: We explore the design of metal binding sites to modulate triple-helix stability of collagen and collagen-mimetic peptides. Globular proteins commonly utilize metals to connect tertiary structural elements that are well separated in sequence, constraining structure and enhancing stability. It is more challenging to engineer structural metals into fibrous protein scaffolds, which lack the extensive tertiary contacts seen in globular proteins. In the collagen triple helix, the structural adjacency of the carboxy-termini of the three chains makes this region an attractive target for introducing metal binding sites. We engineered His3 sites based on structural modeling constraints into a series of designed homotrimeric and heterotrimeric peptides, assessing the capacity of metal binding to improve stability and in the case of heterotrimers, affect specificity of assembly. Notable enhancements in stability for both homo- and heteromeric systems were observed upon addition of zinc(II) and several other metal ions only when all three histidine ligands were present. Metal binding affinities were consistent with the expected Irving-Williams series for imidazole. Unlike other metals tested, copper(II) also bound to peptides lacking histidine ligands. Acetylation of the peptide N-termini prevented copper binding, indicating proline backbone amide metal-coordination at this site. Copper similarly stabilized animal extracted Type I collagen in a metal-specific fashion, highlighting the potential importance of metal homeostasis within the extracellular matrix.
authors.forename: Avanish S
authors.initials: AS
authors.lastname: Parmar
authors.forename: Fei
authors.initials: F
authors.lastname: Xu
authors.forename: Douglas H
authors.initials: DH
authors.lastname: Pike
authors.forename: Sandeep V
authors.initials: SV
authors.lastname: Belure
authors.forename: Nida F
authors.initials: NF
authors.lastname: Hasan
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Drzewiecki
authors.forename: David I
authors.initials: DI
authors.lastname: Shreiber
authors.forename: Vikas
authors.initials: V
authors.lastname: Nanda
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D024042:Collagen Type I / Q000737:chemistry* / Q000378:metabolism*; D003300:Copper / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D008667:Metalloproteins / Q000737:chemistry / Q000235:genetics; D008670:Metals / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D008958:Models, Molecular; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry / Q000235:genetics; D015202:Protein Engineering; D055550:Protein Stability / Q000187:drug effects; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary
chemical_list: D024042:Collagen Type I; D008667:Metalloproteins; D008670:Metals; D010455:Peptides; D003300:Copper