title: Molecular analysis of a gene encoding a serum-resistance-associated 76 kDa surface antigen of Haemophilus somnus.
abstract: Haemophilus somnus is a Gram-negative bacterial bovine pathogen which can cause disease or be carried asymptomatically. We previously showed that four serum-sensitive isolates from asymptomatic carriers lacked a 13.4 kb sequence of chromosomal DNA that was present in two virulent serum-resistant strains. We have since sequenced 5 kb of the 13.4 kb fragment from a serum-resistant strain, which contained an open reading frame (ORF) of at least 4.5 kb. From Western blot analysis, the ORF was shown to encode a 76 kDa protein (p76) that co-migrated with a 76 kDa H. somnus surface protein. Both the recombinant and natural p76 reacted with convalescent-phase serum from a cow in an experimental H. somnus abortion study. The translational start site for p76 was identified by deletion analysis of subclones of the 5 kb cloned sequence. The 4.5 kb ORF contained 1.2 kb tandem direct repeats (DRs), with 65% identity between the two repeats at the protein level. The 5' DR (DR1) included the start site for the 76 kDa protein, and DR2 had a flanking inverted repeat, suggestive of an insertion-sequence-like element.
authors.affiliation: Department of Pathology, University of California San Diego Medical Center 92103-8416.
authors.forename: S P
authors.initials: SP
authors.lastname: Cole
authors.forename: D G
authors.initials: DG
authors.lastname: Guiney
authors.forename: L B
authors.initials: LB
authors.lastname: Corbeil
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000942:Antigens, Bacterial / Q000737:chemistry / Q000235:genetics*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D001483:Base Sequence; D002417:Cattle; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D006190:Haemophilus / Q000235:genetics* / Q000276:immunology* / Q000472:pathogenicity; D008969:Molecular Sequence Data; D008970:Molecular Weight; D012091:Repetitive Sequences, Nucleic Acid; D014774:Virulence / Q000235:genetics / Q000276:immunology
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial