title: Specific aspartic acid-rich sequences are responsible for silver staining of nucleolar proteins.
abstract: Ag-NOR proteins are silver-stainable proteins in the nucleolar organizer regions and are used to distinguish benign from malignant tumors. B23 and C23 are the two major Ag-NOR proteins. This study shows that only one of the two acidic clusters of B23 is responsible for its silver staining property. Fusion of this region of B23 (amino acids 161-188) to glutathione S-transferase produced an Ag-NOR positive fusion protein. The same result was obtained when amino acids 233-277 of C23 was fused with glutathione S-transferase. The aspartate residues, but not the glutamate residues, were found to be primarily responsible for the silver staining of the acidic clusters.
authors.affiliation: Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030.
authors.forename: B C
authors.initials: BC
authors.lastname: Valdez
authors.forename: D
authors.initials: D
authors.lastname: Henning
authors.forename: T V
authors.initials: TV
authors.lastname: Le
authors.forename: H
authors.initials: H
authors.lastname: Busch
mesh_terms: D000595:Amino Acid Sequence; D001224:Aspartic Acid; D002466:Cell Nucleolus / Q000648:ultrastructure*; D003001:Cloning, Molecular; D003937:Diagnosis, Differential; D004926:Escherichia coli; D005982:Glutathione Transferase / Q000032:analysis / Q000096:biosynthesis; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009369:Neoplasms / Q000473:pathology / Q000648:ultrastructure; D009687:Nuclear Proteins / Q000032:analysis* / Q000096:biosynthesis / Q000737:chemistry*; D009697:Nucleolus Organizer Region / Q000648:ultrastructure; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000096:biosynthesis / Q000737:chemistry; D017384:Sequence Deletion; D012834:Silver; D013194:Staining and Labeling
chemical_list: D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D001224:Aspartic Acid; D012834:Silver; D005982:Glutathione Transferase