title: The solution structure of a chimeric LEKTI domain reveals a chameleon sequence.
abstract: The conversion of an alpha-helical to a beta-strand conformation and the presence of chameleon sequences are fascinating from the perspective that such structural features are implicated in the induction of amyloid-related fatal diseases. In this study, we have determined the solution structure of a chimeric domain (Dom1PI) from the multidomain Kazal-type serine proteinase inhibitor LEKTI using multidimensional NMR spectroscopy. This chimeric protein was constructed to investigate the reasons for differences in the folds of the homologous LEKTI domains 1 and 6 [Lauber, T., et al. (2003) J. Mol. Biol. 328, 205-219]. In Dom1PI, two adjacent phenylalanine residues (F28 and F29) of domain 1 were substituted with proline and isoleucine, respectively, as found in the corresponding P4' and P5' positions of domain 6. The three-dimensional structure of Dom1PI is significantly different from the structure of domain 1 and closely resembles the structure of domain 6, despite the sequence being identical to that of domain 1 except for the two substituted phenylalanine residues and being only 31% identical to the sequence of domain 6. The mutation converted a short 3(10)-helix into an extended loop conformation and parts of the long COOH-terminal alpha-helix of domain 1 into a beta-hairpin structure. The latter conformational change occurs in a sequence stretch distinct from the region containing the substituted residues. Therefore, this switch from an alpha-helical structure to a beta-hairpin structure indicates a chameleon sequence of seven residues. We conclude that the secondary structure of Dom1PI is determined not only by the local protein sequence but also by nonlocal interactions.
authors.affiliation: Lehrstuhl für Biopolymere, Universität Bayreuth, Universitätsstrasse 30, 95447 Bayreuth, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Tidow
authors.forename: Thomas
authors.initials: T
authors.lastname: Lauber
authors.forename: Klaus
authors.initials: K
authors.lastname: Vitzithum
authors.forename: Christian P
authors.initials: CP
authors.lastname: Sommerhoff
authors.forename: Paul
authors.initials: P
authors.lastname: Rösch
authors.forename: Ute C
authors.initials: UC
authors.lastname: Marx
mesh_terms: D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics; D005341:Fibrinolysin / Q000037:antagonists & inhibitors; D005813:Genes, Synthetic / Q000235:genetics; D006801:Humans; D006868:Hydrolysis; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D009842:Oligopeptides / Q000737:chemistry* / Q000235:genetics; D017510:Protein Folding; D017433:Protein Structure, Secondary / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D053491:Proteinase Inhibitory Proteins, Secretory; D011506:Proteins / Q000737:chemistry* / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000235:genetics; D000074163:Serine Peptidase Inhibitor Kazal-Type 5; D012996:Solutions; D013381:Subtilisins / Q000037:antagonists & inhibitors; D014361:Trypsin Inhibitors / Q000737:chemistry / Q000235:genetics
chemical_list: D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D009842:Oligopeptides; D053491:Proteinase Inhibitory Proteins, Secretory; D011506:Proteins; D011993:Recombinant Fusion Proteins; C120650:SPINK5 protein, human; D000074163:Serine Peptidase Inhibitor Kazal-Type 5; D012996:Solutions; D014361:Trypsin Inhibitors; C099159:chameleon alpha protein, synthetic; C099160:chameleon beta protein, synthetic; D013381:Subtilisins; D005341:Fibrinolysin