title: Monosaccharide templates for de novo designed 4-alpha-helix bundle proteins: template effects in carboproteins.
abstract: De novo design and total chemical synthesis of proteins provide powerful approaches to critically test our understanding of protein folding, structure, and stability. The 4-alpha-helix bundle is a frequently studied structure in which four amphiphilic alpha-helical peptide strands form a hydrophobic core. Assembly of protein models on a template has been suggested as a way to reduce the entropy of folding. We have previously developed the concept of carbohydrates as templates in the de novo design of protein models termed 'carboproteins'. Here we present the chemical synthesis of three 8.1 kDa 4-alpha-helix bundles by oxime ligation of tetra-aminooxyacetyl functionalized D-galacto-, D-gluco-, and D-altropyranoside templates with an amphiphilic C-terminal hexadecapeptide aldehyde sequence. CD spectroscopy indicated that the choice of template has an effect on the overall structure of the carboprotein, as the altro-based carboprotein was found to be more alpha-helical than the corresponding galacto- and gluco-carboproteins. However, an influence on stability could not be detected in the present experiments, as the three carboproteins gave similar free energy of foldings (deltaG(F)H2O) and melting points in chemical and thermal denaturation experiments.
authors.affiliation: Department of Chemistry, Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg, Denmark.
authors.forename: Jesper
authors.initials: J
authors.lastname: Brask
authors.forename: Jan M
authors.initials: JM
authors.lastname: Dideriksen
authors.forename: John
authors.initials: J
authors.lastname: Nielsen
authors.forename: Knud J
authors.initials: KJ
authors.lastname: Jensen
mesh_terms: D002241:Carbohydrates / Q000737:chemistry; D015394:Molecular Structure; D009005:Monosaccharides / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000138:chemical synthesis / Q000737:chemistry*; D011714:Pyrans / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D013696:Temperature
chemical_list: D002241:Carbohydrates; D009005:Monosaccharides; D010455:Peptides; D011506:Proteins; D011714:Pyrans