title: Repeated sequence elements in the high molecular weight basic nuclear proteins from the winter flounder.
abstract: In maturing sperm of the winter flounder, histones are not replaced by protamines but instead joined by a group of high molecular weight basic nuclear proteins. Despite their large size and number of components, these proteins were reduced to a relatively simple set of peptides by a "limit" digestion with endoprotease Lys-C. Nine of these peptides, that together account for half of the mass of the digest, were purified by two rounds of chromatography on a C18 reverse-phase high pressure liquid chromatographic column and analysed by sequential Edman degradation. Their sequences can be divided into two homology groups. Seven of the peptides contain all or part of a dodecapeptide consensus sequence, NH2-Ser-Pro-Met-Arg-Ser-Arg-Ser-Pro-Ser-Arg-Ser-Lys-COOH, which appears to be tandemly repeated. This dodecapeptide contains a previously recognized consensus phosphorylation sequence, NH2-Arg-Ser-Arg-Ser-Pro-COOH, in which both serines are phosphorylated during the early stages of spermiogenesis. The other homology group has the sequence NH2-Arg-Arg-Val-X-X-Pro-Lys-COOH, where X-X is either Gln-Thr or Pro-Ser. The dodecapeptide and heptapeptide sequences form at least 35 and 11%, respectively, of the high molecular weight basic nuclear proteins and are, therefore, repeated many times over in these proteins. A search for identical or homologous sequences within the Protein Sequence Database indicated that they are unique. The closest matches were to protamines and some viral DNA-binding proteins.
authors.affiliation: Department of Biochemistry, Queen's University, Kingston, Ont., Canada.
authors.forename: D C
authors.initials: DC
authors.lastname: Young
authors.forename: P L
authors.initials: PL
authors.lastname: Davies
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D010450:Endopeptidases; D005412:Flatfishes / Q000378:metabolism*; D005432:Flounder / Q000378:metabolism*; D008666:Metalloendopeptidases; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000032:analysis*
chemical_list: D009687:Nuclear Proteins; D010450:Endopeptidases; D008666:Metalloendopeptidases; C039830:peptidyl-Lys metalloendopeptidase