4W4J

Crystal structure of EspG3 from the ESX-3 type VII secretion system of M. smegmatis

Summary for 4W4J

• Entry DOI: 10.2210/pdb4w4j/pdb
• Related: 4W4I 4W4K 4W4L
• Descriptor: EspG3, SULFATE ION (2 entities in total)
• Functional Keywords: signal recognition, virulence factor, protein secretion, adaptor, protein transport
• Biological source: Mycobacterium smegmatis
• Total number of polymer chains: 2
• Total formula weight: 68268.74

Authors

Ekiert, D.C.,Cox, J.S. (deposition date: 2014-08-14, release date: 2014-10-01, Last modification date: 2024-11-06)

Primary citation

Ekiert, D.C.,Cox, J.S.
Structure of a PE-PPE-EspG complex from Mycobacterium tuberculosis reveals molecular specificity of ESX protein secretion.
Proc.Natl.Acad.Sci.USA, 111:14758-14763, 2014

PubMed Abstract: Nearly 10% of the coding capacity of the Mycobacterium tuberculosis genome is devoted to two highly expanded and enigmatic protein families called PE and PPE, some of which are important virulence/immunogenicity factors and are secreted during infection via a unique alternative secretory system termed "type VII." How PE-PPE proteins function during infection and how they are translocated to the bacterial surface through the five distinct type VII secretion systems [ESAT-6 secretion system (ESX)] of M. tuberculosis is poorly understood. Here, we report the crystal structure of a PE-PPE heterodimer bound to ESX secretion-associated protein G (EspG), which adopts a novel fold. This PE-PPE-EspG complex, along with structures of two additional EspGs, suggests that EspG acts as an adaptor that recognizes specific PE-PPE protein complexes via extensive interactions with PPE domains, and delivers them to ESX machinery for secretion. Surprisingly, secretion of most PE-PPE proteins in M. tuberculosis is likely mediated by EspG from the ESX-5 system, underscoring the importance of ESX-5 in mycobacterial pathogenesis. Moreover, our results indicate that PE-PPE domains function as cis-acting targeting sequences that are read out by EspGs, revealing the molecular specificity for secretion through distinct ESX pathways.

PubMed: 25275011
DOI: 10.1073/pnas.1409345111

Experimental method

X-RAY DIFFRACTION (2.803 Å)