title: Helical structure of basic proteins from spermatozoa. Comparison with model peptides.
abstract: We describe structural studies carried out with some basic proteins found in association with DNA in the spermatozoa of molluscs and echinoderms. We have studied proteins related to histone H1 as well as protamines. Structural prediction methods show that these proteins have a strong helical potential and contain several turns, mainly of the SPKK type. No beta structures were found. Strong structural similarities have been detected between distantly related species. The presence of helical regions is confirmed by circular dichroism in trifluoroethanol solution. The influence of the SPKK turns is also evident in the CD spectra. In proteins which contain a high percentage of arginine we conclude that conventional prediction methods should be modified in order to allow for a higher helical potential for this amino acid residue. Synthetic peptides with a sequence present in the C-terminal region of histone H1 have also been studied. It was found that octapeptides may only acquire a small amount of structure, whereas hexadecapeptides are 50-60% helical. These studies strongly suggest that both protamines and proteins related to the C-terminal part of histone H1 interact with DNA mainly in the alpha-helical conformation.
authors.affiliation: Departament d'Enginyeria Química, ETSEIB, Universitat Politècnica de Catalunya, Barcelona, Spain.
authors.forename: N
authors.initials: N
authors.lastname: Verdaguer
authors.forename: M
authors.initials: M
authors.lastname: Perelló
authors.forename: J
authors.initials: J
authors.lastname: Palau
authors.forename: J A
authors.initials: JA
authors.lastname: Subirana
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D004447:Echinodermata / Q000737:chemistry*; D006657:Histones / Q000737:chemistry; D008297:Male; D008956:Models, Chemical; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D008974:Mollusca / Q000737:chemistry*; D009687:Nuclear Proteins / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D011479:Protamines / Q000737:chemistry; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D013094:Spermatozoa / Q000737:chemistry*
chemical_list: D006657:Histones; D009687:Nuclear Proteins; D010455:Peptides; D011479:Protamines