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Structure of the reovirus membrane-penetration protein, Mu1, in a complex with is protector protein, Sigma3

Susanne Liemann1, Kartik Chandran, Timothy S Baker

  • 1Howard Hughes Medical Institute, Children's Hospital, Harvard Medical School, 320 Longwood Avenue, Boston, MA 02115, USA.

Cell
|February 8, 2002
PubMed

Insights

Nonenveloped viruses like reovirus use the Mu1 protein to penetrate host cells. A "myristoyl switch" mechanism, involving protein cleavage and rearrangement, facilitates this membrane entry.

Area of Science:

  • Virology
  • Structural Biology
  • Biochemistry

Background:

  • Nonenveloped viruses enter cells via membrane penetration, distinct from membrane fusion.
  • The reovirus outer-capsid protein Mu1 is crucial for this penetration process.

Purpose of the Study:

  • To elucidate the molecular mechanism of viral membrane penetration by reovirus.
  • To determine the structural basis of the Mu1 protein's role in cell entry.

Main Methods:

  • Cryo-electron microscopy (cryo-EM) to visualize the intact virion.
  • Structural analysis of the Mu1-Sigma3 heterohexameric complex.
  • Biochemical characterization of Mu1 autolytic cleavage.

Main Results:

  • The structure of the Mu1(3)Sigma3(3) complex was determined and fitted into the cryo-EM image of the virion.
  • Mu1 undergoes autolytic cleavage into Mu1N and Mu1C, with Mu1N dissociating.
  • A conformational change in the Mu1 trimer precedes myristoylation and membrane insertion.

Conclusions:

  • A "myristoyl switch" mechanism is proposed for viral penetration.
  • This mechanism involves myristoyl group exposure, Mu1N cleavage, and Mu1C rearrangement.
  • Understanding this process is key to viral entry mechanisms.

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