title: Molecular features governing the stability and specificity of functional complex formation by Mycobacterium tuberculosis CFP-10/ESAT-6 family proteins.
abstract: The Mycobacterium tuberculosis complex CFP-10/ESAT-6 family proteins play essential but poorly defined roles in tuberculosis pathogenesis. In this article we report the results of detailed spectroscopic studies of several members of the CFP-10/ESAT-6 family. This work shows that the CFP-10/ESAT-6 related proteins, Rv0287 and Rv0288, form a tight 1:1 complex, which is predominantly helical in structure and is predicted to closely resemble the complex formed by CFP-10 and ESAT-6. In addition, the Rv0287.Rv0288 complex was found to be significantly more stable to both chemical and temperature induced denaturation than CFP-10.ESAT-6. This approach demonstrated that neither Rv0287.Rv0288 nor the CFP-10.ESAT-6 complexes are destabilized at low pH (4.5), indicating that even in low pH environments, such as the mature phagosome, both Rv0287.Rv0288 and CFP-10.ESAT-6 undoubtedly function as complexes rather than individual proteins. Analysis of the structure of the CFP-10.ESAT-6 complex and optimized amino acid sequence alignments of M. tuberculosis CFP-10/ESAT-6 family proteins revealed that residues involved in the intramolecular contacts between helices are conserved across the CFP-10/ESAT-6 family, but not those involved in primarily intermolecular contacts. This analysis identified the molecular basis for the specificity and stability of complex formation between CFP-10/ESAT-6 family proteins, and indicates that the formation of functional complexes with key roles in pathogenesis will be limited to genome partners, or very closely related family members, such as Rv0287/Rv0288 and Rv3019c/Rv3020c.
authors.affiliation: Department of Biochemistry, Henry Wellcome Building, University of Leicester, Leicester, LE1 9HN, United Kingdom.
authors.forename: Kirsty L
authors.initials: KL
authors.lastname: Lightbody
authors.forename: Dariush
authors.initials: D
authors.lastname: Ilghari
authors.forename: Lorna C
authors.initials: LC
authors.lastname: Waters
authors.forename: Gemma
authors.initials: G
authors.lastname: Carey
authors.forename: Mark A
authors.initials: MA
authors.lastname: Bailey
authors.forename: Richard A
authors.initials: RA
authors.lastname: Williamson
authors.forename: Philip S
authors.initials: PS
authors.lastname: Renshaw
authors.forename: Mark D
authors.initials: MD
authors.lastname: Carr
mesh_terms: D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry*; D002942:Circular Dichroism; D008954:Models, Biological; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000378:metabolism*; D010588:Phagosomes / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C117940:CFP-10 protein, Mycobacterium tuberculosis; C093276:ESAT-6 protein, Mycobacterium tuberculosis; C505464:ESAT-6-CFP10 fusion protein; D011993:Recombinant Fusion Proteins