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Title page. * RSV Core Assembly: It ’ s All About Nucleation. Carmen Butan, Giovanni Cardone, Naiqian Cheng, Bernard Heymann, Paul Keller, Dennis Winkler. Laboratory of Structural Biology, NIAMS-NIH. Parvez Lokhandwala, John Purdy, Rebecca Craven. - PowerPoint PPT Presentation
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Carmen Butan, Giovanni Cardone, Naiqian Cheng,
Bernard Heymann, Paul Keller, Dennis Winkler
Laboratory of Structural Biology, NIAMS-NIH
Parvez Lokhandwala, John Purdy, Rebecca Craven
Pennsylvania State University College of Medicine
* RSV Core Assembly: It’s All About Nucleation
Retroviruses are highly variable in their capsid architecture, both for a given retrovirus and between different retroviruses. With HIV, the predominant capsid morphology is biconical; with Rous sarcoma virus, it is irregular polyhedra. Cylindrical tubes with and without end-caps are also produced.
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Butan et al. (2008) J. Mol. Biol., 376, 1168-81
Cryo-electron tomogram of Rous sarcoma virus
Angular, curved and miscellaneous cores
Virions with angular cores have many spikes: Virions with tubular cores have few spikes
In retroviruses, the capsid assembles de novoinside the provirion, post-budding
Not all of the capsid protein assembles: > 50% remains unassembled (Prevelige et al; Fuller et al)
Angular cores correlate with high CA assembly efficiencies: Tubular cores correlate with low CA assembly efficiencies
Measure #Gag ( total # CA) from
virion diameter
Observations
- tubular cores and many “curved”cores - including biconical RSVcores - fail to package RNP
- The range of polymorphic variation is very large
- Hypothesis: a viable core is one that is closed and has successfully packaged the genome(s) and the polymerase
Observations
- tubular cores and many “curved”cores - including biconical RSVcores - fail to package RNP
- The range of polymorphic variation is very large
- Hypothesis: a viable core is one that is closed and has successfully packaged the genome(s) and the polymerase
- Inference: Initiation is key to capsid assembly
Critical concentrations for assembly
Total conc’n of protein subunits
conc
’n o
f pro
tein
sub
units
in c
apsi
ds
Nucleation of angular nucleocapsid assembly : a model