Virion structure

AIDS virion structure. Numbers associated with proteins are kilodalton masses (e.g., gpl20 is a 120-kd protein). ( Scientific American, Inc., George V. Kelvin. Reprinted by permission.)... 

Combining these two approaches, by determining the crystal structure of individual subcomponents and fitting these into the lower resolution maps of intact particles, may offer the best current hope for obtaining high-resolution information about virion structure. An example of this is provided by adenovirus, where the crystal structure of the hexon, formed by three copies of the 100-kDa major structural protein, has been fitted into a low-resolution capsid structure determined by electron cryomicro-scopy to provide a clearer picture of capsid organization and information about the locations of minor capsid proteins (Stewart et al, 1993). A similar strategy has been used to fit the crystal structure of a portion of the HSV-1 major capsid protein (VPS) into an intermediate-resolution map of the capsid (B. Bowman, personal communication). 

Prasad and Prevelige, Fig. 3. Summary of the architectural features of rotavirus, a prototypical member of the Reoviridae family, (a) Cutaway of the mature virion structure, showing the locations of the various structural proteins, (b) Cutaway of the transcriptionally competent double-layered particle, showing the RNA core. (c). Structure of actively transcribing rotavirus double-layered particles, (d) Close-up of the exit pathway of the mRNA during transcription (Lawton et at, 1997). (e) Model for the organization of the RNA segments (Pesavento et at, 2001). 

The retrovirus genome has three regions, gag, pol, and env, that encode proteins, and all of these proteins are found in the virion. The gag region encodes a polyprotein that is cleaved to form internal virion structural proteins. The pol... 

GPC proved of great value in the preparation of viral proteins, because the fractions obtained could be subjected to further analysis. A study of viral proteins is of interest from the point of view of not only the virion structure but also the immunological properties. 

STRUCTURE AND REPLICATION OF ALPHAVIRUSES Virion Structure Replication... 

Week and Wagner (1979a) analyzed RNA metabolism in MPC-11 cells infected with various temperature-sensitive (ts) mutants and 5 -defective-interfering particles which cannot synthesize mRNA. A group I mutant, /sG114, restricted in transcriptional activities (Hunt et al., 1976), failed to shut-off host cell RNA metabolism in MPC-11 cells incubated at the restrictive temperature of 39°C for 4 hr. At the permissive temperature (3rC), all mutants (including /5G114) were as effective as the wild-type virus in the shut-off of RNA synthesis. Because tjG 114(1) did not inhibit cell RNA metabolism at the non-permissive temperature, it was used to test for a virion structural... 

Thus, it appears that a normal complement of the final virion structural polypeptides El, E2, and C is not required for the cellular protein inhibition, although intermediate cleavage products or an uncleaved precursor polypeptide may be involved. Which virus-specific polypeptide is responsible for damaging the sodium pump and altering the permeability of the host cell membrane can only be determined by further experimentation. 

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