title: The 18-kilodalton Chlamydia trachomatis histone H1-like protein (Hc1) contains a potential N-terminal dimerization site and a C-terminal nucleic acid-binding domain.
abstract: The Chlamydia trachomatis histone H1-like protein (Hc1) is a DNA-binding protein specific for the metabolically inactive chlamydial developmental form, the elementary body. Hc1 induces DNA condensation in Escherichia coli and is a strong inhibitor of transcription and translation. These effects may, in part, be due to Hc1-mediated alterations of DNA topology. To locate putative functional domains within Hc1, polypeptides Hc1(2-57) and Hc1(53-125), corresponding to the N- and C-terminal parts of Hc1, respectively, were generated. By chemical cross-linking with ethylene glycol-bis (succinic acid N-hydroxysuccinimide ester), purified recombinant Hc1 was found to form dimers. The dimerization site was located in the N-terminal part of Hc1 (Hc1(2-57)). Moreover, circular dichroism measurements indicated an overall alpha-helical structure of this region. By using limited proteolysis, Southwestern blotting, and gel retardation assays, Hc1(53-125) was shown to contain a domain capable of binding both DNA and RNA. Under the same conditions, Hc1(2-57) had no nucleic acid-binding activity. Electron microscopy of Hc1-DNA and Hc1(53-125)-DNA complexes revealed differences suggesting that the N-terminal part of Hc1 may affect the DNA-binding properties of Hc1.
authors.affiliation: Department of Medical Microbiology and Immunology, University of Aarhus, Denmark.
authors.forename: L B
authors.initials: LB
authors.lastname: Pedersen
authors.forename: S
authors.initials: S
authors.lastname: Birkelund
authors.forename: A
authors.initials: A
authors.lastname: Holm
authors.forename: S
authors.initials: S
authors.lastname: Ostergaard
authors.forename: G
authors.initials: G
authors.lastname: Christiansen
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002692:Chlamydia trachomatis / Q000737:chemistry* / Q000235:genetics; D002942:Circular Dichroism; D003001:Cloning, Molecular; D003432:Cross-Linking Reagents; D004247:DNA / Q000378:metabolism / Q000648:ultrastructure; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D006657:Histones / Q000737:chemistry; D015151:Immunoblotting; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D015800:Protozoan Proteins; D012313:RNA / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017421:Sequence Analysis; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins; C088071:Hc1 protein, Chlamydia trachomatis; D006657:Histones; D010446:Peptide Fragments; D015800:Protozoan Proteins; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D012313:RNA; D004247:DNA