The coat protein of Rabbit hemorrhagic disease virus contains a molecular switch at the N-terminal region facing the inner surface of the capsid.
To function adequately, many if not all proteins involved in macromolecular assemblies show conformational polymorphism as an intrinsic feature. This general strategy has been described for many essential cellular processes. Here we describe this structural polymorphism in a viral protein, the coat protein of Rabbit hemorrhagic disease virus (RHDV), which is required during virus capsid assembly. By combining genetic, structure modeling, and cryo-electron microscopy and image processing analysis, we have established the mechanism that allows RHDV coat protein to switch among quasi-equivalent conformational states to achieve the appropriate curvature for the formation of a closed shell. The RHDV capsid structure is based on a T = 3 lattice, containing 180 copies of identical subunits, similar to those of other caliciviruses. The quasi-equivalent interactions between the coat proteins are achieved by the N-terminal region of a subset of subunits, which faces the inner surface of the capsid shell. Mutant coat protein lacking this N-terminal sequence assembles into T = 1 capsids. Our results suggest that the polymorphism of the RHDV T = 3 capsid might bear resemblance to that of plant virus T = 3 capsids.
Bárcena
Juan
J
Centro de Investigación en Sanidad Animal (CISA-INIA), Valdeolmos, 28130, Madrid, Spain.
Verdaguer
Nuria
N
Roca
Ramón
R
Morales
Mónica
M
Angulo
Iván
I
Risco
Cristina
C
Carrascosa
José L
JL
Torres
Juan M
JM
Castón
José R
JR
D000595:Amino Acid Sequence; D002213:Capsid / Q000737:chemistry*; D036022:Capsid Proteins / Q000737:chemistry* / Q000235:genetics; D017929:Hemorrhagic Disease Virus, Rabbit / Q000737:chemistry* / Q000502:physiology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D015678:Viral Structural Proteins / Q000737:chemistry* / Q000235:genetics; D019065:Virus Assembly
D036022:Capsid Proteins; D015678:Viral Structural Proteins; C081149:viral protein 60, rabbit hemorrhagic disease virus