title: PL-I of Spisula solidissima, a highly elongated sperm-specific histone H1.
abstract: The major chromosomal protein of the mature sperm of the surf clam, Spisula solidissima, is a histone H1-related protamine-like (PL-I) protein of low electrophoretic mobility. We report here the complete sequence of two isoforms of its encoding genes. These genes encode a protein of 453 and 454 amino acids, respectively. The predicted mass of the larger isoforms (51,437 Da) was confirmed using electrospray ionization mass spectrometry. The amino-terminal tail of the S. solidissima PL-I is greatly elongated because of the presence of 39 tandem hexapeptide repeats of the motif (K/R)KRSAS with a few semiconservative amino acid substitutions. These repeats are very closely mirrored by their encoding DNA sequence, which indicates that an expansion because of sequence duplication most likely occurred. The C-terminal domain consists of a histone H1-related core with a predicted winged-helix tertiary structure, which is followed by an unstructured lysine-rich tail. This information provides additional molecular support for the classification and underlying evolution of sperm nuclear basic proteins in bivalve molluscs.
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada, V8W 3P6.
authors.forename: John D
authors.initials: JD
authors.lastname: Lewis
authors.forename: Reginald
authors.initials: R
authors.lastname: McParland
authors.forename: Juan
authors.initials: J
authors.lastname: Ausió
mesh_terms: D020413:3' Untranslated Regions; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D049872:Bivalvia / Q000378:metabolism*; D017931:DNA Primers; D006657:Histones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008297:Male; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D013094:Spermatozoa / Q000378:metabolism*
chemical_list: D020413:3' Untranslated Regions; D017931:DNA Primers; D006657:Histones