title: A human gene (AHNAK) encoding an unusually large protein with a 1.2-microns polyionic rod structure.
abstract: We report here the identification and partial characterization of a human gene (designated AHNAK) that encodes an unusually large protein (approximately 700 kDa). AHNAK is expressed by means of a 17.5-kilobase mRNA in diverse cellular lineages but is typically repressed in cell lines derived from human neuroblastomas and in several other types of tumors. Unique-sequence domains at the two ends of the protein flank a large internal domain (approximately 4300 amino acids) composed of highly conserved repeated elements, most of which are 128 amino acids in length. The repeated elements in turn display a redundant motif, marked by the recurrence of proline at every seventh residue. Within these sequences, hydrophobic and hydrophilic residues alternate in a manner that is incompatible with a helical coiled-coil structure. Instead, we propose a structure resembling a beta-strand but with a periodicity of 2.33. The structure would engender a polyionic rod approximately 1.2 microns long. Preliminary evidence indicates that the protein resides predominantly within the nucleus, but no function has yet been discerned.
authors.affiliation: George Williams Hooper Research Foundation, Department of Microbiology and Immunology, University of California, San Francisco 94143.
authors.forename: E
authors.initials: E
authors.lastname: Shtivelman
authors.forename: F E
authors.initials: FE
authors.lastname: Cohen
authors.forename: J M
authors.initials: JM
authors.lastname: Bishop
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000235:genetics; D000595:Amino Acid Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D004273:DNA, Neoplasm / Q000235:genetics / Q000302:isolation & purification; D005796:Genes; D006801:Humans; D008565:Membrane Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000235:genetics*; D009447:Neuroblastoma / Q000235:genetics; D010673:Pheochromocytoma / Q000235:genetics; D011487:Protein Conformation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015183:Restriction Mapping
chemical_list: C075176:AHNAK protein, human; D004273:DNA, Neoplasm; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger