title: A molecular switch in the capsid protein controls the particle polymorphism in an icosahedral virus.
abstract: The recombinant coat protein (CP) of Sesbania mosaic virus (SeMV; genus Sobemovirus) was found to self-assemble into capsids encapsidating 23S rRNA and CP mRNA in Escherichia coli. The CP lacking 22 amino acids from the N-terminus assembled into stable T = 3 capsids that appeared similar to SeMV, indicating that the N-terminal 22 amino acid residues are dispensable for T = 3 assembly. Two distinct capsids, T = 1 and pseudo T = 2, were observed when the N-terminal 36 amino acids encompassing the arginine-rich motif (N-ARM) were removed. Only T = 1 particles were observed upon deletion of 65 amino acids from the N-terminus, which also included the sequence element for the beta-annulus. These results reveal that N-ARM acts as a molecular switch in regulating T = 3 assembly. Formation of stable pseudo T = 2 particles shows that pentamers of AB dimers could nucleate assembly at icosahedral-5-folds. Capsids assembled from the N-terminally truncated proteins also encapsidated 23S rRNA and CP mRNA, suggesting the presence of sites outside the N-terminal 65 residues that may be involved in RNA--protein interactions.
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India.
authors.forename: G L
authors.initials: GL
authors.lastname: Lokesh
authors.forename: T D S
authors.initials: TD
authors.lastname: Gowri
authors.forename: P S
authors.initials: PS
authors.lastname: Satheshkumar
authors.forename: M R N
authors.initials: MR
authors.lastname: Murthy
authors.forename: H S
authors.initials: HS
authors.lastname: Savithri
mesh_terms: D000595:Amino Acid Sequence; D002213:Capsid / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D015967:Gene Expression Regulation, Viral; D008854:Microscopy, Electron; D008958:Models, Molecular; D011110:Polymorphism, Genetic; D012328:RNA Viruses / Q000235:genetics / Q000378:metabolism*; D014771:Virion / Q000235:genetics / Q000378:metabolism*; D019065:Virus Assembly