title: Identification of two proteins that interact with the Erp virulence factor from Mycobacterium tuberculosis by using the bacterial two-hybrid system.
abstract: BACKGROUND
  The exported repetitive protein (erp) gene encodes a secreted 36-kDa protein with a central domain containing several proline-glycine-leucine-threonine-serine (PGLTS) repeats. It has been demonstrated that erp is a virulence-associated factor since the disruption of this gene impairs the growth of Mycobacterium bovis and Mycobacterium tuberculosis in mice.
  
  
  RESULTS
  In order to elucidate the function of Erp we searched for Erp-binding proteins from M. tuberculosis by using a bacterial two-hybrid system. Our results indicate that Erp interacts specifically with two putative membrane proteins, Rv1417 and Rv2617c. Further analysis revealed that the latter two interact with each other, indicating that Rv1417, Rv2617c and Erp are connected through multiple interactions. While Rv1417 is disseminated in several Actinomycetales genera, orthologues of Rv2617c are exclusively present in members of the M. tuberculosis complex (MTC). The central and amino-terminal regions of Erp were determined to be involved in the interaction with Rv1417 and Rv2627c. Erp forms from Mycobacterium smegmatis and Mycobacterium leprae were not able to interact with Rv2617c in two-hybrid assays. Immunolocalization experiments showed that Rv1417 and Rv2617c are found on the cell membrane and Erp on the bacterial cell wall. Finally, comparative genomics and expression studies revealed a possible role of Rv1417 in riboflavin metabolism.
  
  
  CONCLUSIONS
  We identified interactive partners of Erp, an M. tuberculosis protein involved in virulence, which will be the focus of future investigation to decipher the function of the Erp family protein.
authors.affiliation: Institute of Biotechnology, CICVyA-INTA Castelar, Nicolas Repetto and Los Reseros, 1686, Hurlingham, Argentina. lklepp@cnia.inta.gov.ar
authors.forename: Laura I
authors.initials: LI
authors.lastname: Klepp
authors.forename: Marcelo
authors.initials: M
authors.lastname: Soria
authors.forename: Federico C
authors.initials: FC
authors.lastname: Blanco
authors.forename: María V
authors.initials: MV
authors.lastname: Bianco
authors.forename: María P
authors.initials: MP
authors.lastname: Santangelo
authors.forename: Angel A
authors.initials: AA
authors.lastname: Cataldi
authors.forename: Fabiana
authors.initials: F
authors.lastname: Bigi
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D020869:Gene Expression Profiling; D008565:Membrane Proteins / Q000378:metabolism*; D009166:Mycobacterium leprae / Q000378:metabolism; D020102:Mycobacterium smegmatis / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D001426:Bacterial Proteins; C096737:ERP protein, Mycobacterium tuberculosis; D008565:Membrane Proteins