title: Structures of EccB1 and EccD1 from the core complex of the mycobacterial ESX-1 type VII secretion system.
abstract: BACKGROUND
  The ESX-1 type VII secretion system is an important determinant of virulence in pathogenic mycobacteria, including Mycobacterium tuberculosis. This complicated molecular machine secretes folded proteins through the mycobacterial cell envelope to subvert the host immune response. Despite its important role in disease very little is known about the molecular architecture of the ESX-1 secretion system.
  
  
  RESULTS
  This study characterizes the structures of the soluble domains of two conserved core ESX-1 components - EccB1 and EccD1. The periplasmic domain of EccB1 consists of 4 repeat domains and a central domain, which together form a quasi 2-fold symmetrical structure. The repeat domains of EccB1 are structurally similar to a known peptidoglycan binding protein suggesting a role in anchoring the ESX-1 system within the periplasmic space. The cytoplasmic domain of EccD1has a ubiquitin-like fold and forms a dimer with a negatively charged groove.
  
  
  CONCLUSIONS
  These structures represent a major step towards resolving the molecular architecture of the entire ESX-1 assembly and may contribute to ESX-1 targeted tuberculosis intervention strategies.
authors.affiliation: Department of Molecular & Cellular Biochemistry and Center for Structural Biology, University of Kentucky, 741 South Limestone, Lexington, KY, 40536, USA. jonw7782@gmail.com.|Present address: Department of Molecular Physiology and Biological Physics and The Myles H. Thaler Center for AIDS and Human Retrovirus Research, University of Virginia, Charlottesville, VA, USA. jonw7782@gmail.com.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Wagner
authors.affiliation: UCLA-DOE Institute, University of California Los Angeles, Los Angeles, CA, 90095-1570, USA. sumchan@mbi.ucla.edu.
authors.forename: Sum
authors.initials: S
authors.lastname: Chan
authors.affiliation: Department of Molecular & Cellular Biochemistry and Center for Structural Biology, University of Kentucky, 741 South Limestone, Lexington, KY, 40536, USA. tj.evans@uky.edu.|Present address: Division of Regulatory Services, College of Agriculture, Food and Environment, University of Kentucky, Lexington, KY, USA. tj.evans@uky.edu.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Evans
authors.affiliation: UCLA-DOE Institute, University of California Los Angeles, Los Angeles, CA, 90095-1570, USA. sarakahng@gmail.com.
authors.forename: Sara
authors.initials: S
authors.lastname: Kahng
authors.affiliation: UCLA-DOE Institute, University of California Los Angeles, Los Angeles, CA, 90095-1570, USA. jenniferkim1224@gmail.com.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Kim
authors.affiliation: UCLA-DOE Institute, University of California Los Angeles, Los Angeles, CA, 90095-1570, USA. marbing@mbi.ucla.edu.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Arbing
authors.affiliation: UCLA-DOE Institute, Departments of Biological Chemistry and Chemistry & Biochemistry, and Howard Hughes Medical Institute, University of California Los Angeles, Los Angeles, CA, 90095-1570, USA. david@mbi.ucla.edu.
authors.forename: David
authors.initials: D
authors.lastname: Eisenberg
authors.affiliation: Department of Molecular & Cellular Biochemistry and Center for Structural Biology, University of Kentucky, 741 South Limestone, Lexington, KY, 40536, USA. kkorotkov@uky.edu.
authors.forename: Konstantin V
authors.initials: KV
authors.lastname: Korotkov
mesh_terms: D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry*; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000737:chemistry*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C093276:ESAT-6 protein, Mycobacterium tuberculosis