title: Differential contribution of the repeats to heparin binding of HBHA, a major adhesin of Mycobacterium tuberculosis.
abstract: BACKGROUND
  Tuberculosis remains one of the most important causes of global mortality and morbidity, and the molecular mechanisms of the pathogenesis are still incompletely understood. Only few virulence factors of the causative agent Mycobacterium tuberculosis are known. One of them is the heparin-binding haemagglutinin (HBHA), an important adhesin for epithelial cells and an extrapulmonary dissemination factor. HBHA mediates mycobacterial adherence to epithelial cells via the interactions of its C-terminal, lysine rich repeat domain with sulfated glycoconjugates on the surface of epithelial cells.
  
  
  RESULTS
  Using defined heparin sulfate (HS) analogs, we determined the minimal heparin fragment length for HBHA binding and structural adaptations of the HBHA heparin-binding domain (HBD) upon binding to heparin. The NMR studies show significant shifts of all residues in the HBD upon interaction with heparin, with stronger shifts in the last repeats compared to the upstream repeats, and indicated that the HS fragments with 14 sugar units cover the entire C-terminal lysine-rich domain of HBHA. The differential implication of the repeats is determined by the relative position of prolines and lysines within each repeat, and may contribute to binding specificity. GAG binding induces a non-homogeneous structural rearrangement in the HBD, with stabilization of a nascent α-helix only in the last penta-repeats.
  
  
  CONCLUSIONS
  Mycobacterial HBHA undergoes structural adaptation upon interaction with GAGs, which is likely involved in binding specificities of the adhesin, and mycobacterial pathogens may use HBD polymorphisms for host or organ specificity. Further studies will aim at decoding the complementarity between HBD repeats and HS sequence.
authors.affiliation: INSERM U1019, Lille, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Lebrun
authors.forename: Dominique
authors.initials: D
authors.lastname: Raze
authors.forename: Bernd
authors.initials: B
authors.lastname: Fritzinger
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Wieruszeski
authors.forename: Franck
authors.initials: F
authors.lastname: Biet
authors.forename: Alexander
authors.initials: A
authors.lastname: Dose
authors.forename: Mathieu
authors.initials: M
authors.lastname: Carpentier
authors.forename: Dirk
authors.initials: D
authors.lastname: Schwarzer
authors.forename: Fabrice
authors.initials: F
authors.lastname: Allain
authors.forename: Guy
authors.initials: G
authors.lastname: Lippens
authors.forename: Camille
authors.initials: C
authors.lastname: Locht
mesh_terms: D018829:Adhesins, Bacterial / Q000737:chemistry* / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D006493:Heparin / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009169:Mycobacterium tuberculosis; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020449:Repetitive Sequences, Amino Acid; D013045:Species Specificity; D013816:Thermodynamics
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; C440647:HbhA protein, Mycobacterium tuberculosis; D008565:Membrane Proteins; D009844:Oligosaccharides; D006493:Heparin