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Structure and mechanism of the Nap adhesion complex from the human pathogen Mycoplasma genitalium

David Aparicio1, Margot P Scheffer2, Marina Marcos-Silva3

  • 1Instituto de Biología Molecular de Barcelona (IBMB-CSIC) and Maria de Maeztu Unit of Excellence, Parc Científic de Barcelona, Baldiri Reixac 10, 08028, Barcelona, Spain.

Nature Communications
|June 10, 2020
PubMed

Insights

Mycoplasma genitalium uses its Nap adhesion complex to infect host cells. Structural studies reveal how the Nap complex opens and closes, enabling bacterial attachment and release for sustained infectivity.

Area of Science:

  • Microbiology
  • Structural Biology
  • Infectious Diseases

Background:

  • Mycoplasma genitalium is a significant human pathogen responsible for genitourinary infections like urethritis and pelvic inflammatory disease.
  • The Nap adhesion complex, composed of P110 and P140 proteins, is crucial for M. genitalium's ability to adhere to host epithelial cells and establish infection.

Purpose of the Study:

  • To determine the structural basis of the Nap adhesion complex's function in Mycoplasma genitalium infectivity.
  • To elucidate the conformational changes of the Nap complex that facilitate host cell attachment and detachment.

Main Methods:

  • X-ray crystallography was employed to determine the high-resolution structures of the P140 protein and its complex with the P110 N-terminal domain.
  • Cryo-electron microscopy (cryo-EM) and cryo-electron tomography (cryo-ET) were utilized to visualize the Nap complex in different functional states and cellular contexts.

Main Results:

  • Crystal structures and cryo-EM revealed a closed conformation of the Nap complex, where the sialic acid binding site on P110 is inaccessible.
  • Cryo-ET identified an open conformation of the Nap complex, demonstrating accessibility of the sialic acid binding site.
  • The study identified distinct closed and open conformations of the Nap complex at high resolution (9.8 and 15 Å).

Conclusions:

  • The conformational dynamics of the Nap complex, switching between open and closed states, are essential for the attachment and release mechanism of M. genitalium.
  • This structural and functional understanding provides insights into the pathogenesis of M. genitalium and potential targets for therapeutic intervention.

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