Reoviruses domains

B. Adenovirus, Reovirus, and Phage PRD1 Fiber Head Domains. 99... 

Fig. 1. Schematic drawings of the viruses discussed in this chapter. (A) An icosahe-dral virus with fiber proteins inserted in its pentameric vertices. The gray box denotes domains with known structures for adenovirus, reovirus, and bacteriophage PRD1, in each case containing the head domain and proximal part of the triple /8-spiral shaft domain. (B) Contractile-tailed bacteriophage T4. T4 contains three different fibrous proteins, fibritin connected to the neck, the long (bent) fibers connected to the base plate, and the short fibers also connected to the base plate. Only two of each of the trimeric fibrous proteins are shown for clarity. The gray box denotes domains with known structure for the T4 short fiber.

More recently, triple /1-spiral repeats have been identified in mammalian reovirus type 3 fiber (Chappell et al., 2002 Fig. 4A), avian reovirus fiber (Guardado Calvo et al., 2005 Fig. 4B), and bacteriophage PRD1 P5 protein (Merckel et al., 2005 Fig. 4C). In the latter two cases, it appears that only two repeats are present, just N-terminal to the head domain. Mammalian reovirus fiber contains eight putative triple /1-spiral repeats, of which three were resolved in the crystal structure (Chappell et al., 2002). 

Guardado Calvo, P., Fox, G. C., Hermo Parrado, X. L., Llamas-Saiz, A. L., Costas, C., Martinez-Costas, J., Benavente, J., and van Raaij, M. J. (2005). Structure of the carboxy-terminal receptor-binding domain of avian reovirus fibre sigmaC. / Mol. Biol. 354, 137-149. 

Depicted here in this cartoon is a representation of various domains of the reovirus hemagglutinin. Some domains are overlapping whereas others are separate and unique from all the rest. The G5 domain appears to be the most relevant to the immune response and also for tropism. 

The anti-idiotypes in the reovirus system resemble hemagglutinin neutralization domains. Functionally shown here is the consequence of administering monoclonal anti-idiotypic proteins to mice. A variety of reovirus specific immune reactivities are induced. 

The fxS protein is associated with the fil protein, and a complex of these proteins has been determined (Liemann et al., 2002). /il forms a T=13 layer in the reovirus particles but is not present in the crystal structure of the capsid (Reinisch et al., 2000). The protein is similar to OrbivirusYPl in that it has a jelly-roll domain positioned external to a base formed mostly by helices. The jelly-roll domain contains a few extra strands, and in the sequence it is flanked by the residues forming the helical region. Although this is true also for the corresponding region in VP7 of bluetongue virus, the fold in this part of the protein is different. 

Chappell, J. D., Gunn, V. L., Wetzel, J. D., Baer, G. S., and Dermody, T. S. (1997). Mutations in type 3 reovirus that determine binding to sialic acid are contained in the fibrous tail domain of viral attachment crl./. Virol. 71, 1834-1841. 

Chapman and Liljas, Fig. 12. The shell-forming proteins of bluetongue virus and reovirus (a) bluetongue VPS protein (Grimes et al, 1998) (b) reovirus 11 protein (Reinisch et al., 2000). In the bluetongue VPS protein, three domains (apical, carapace, and dimerization domains) have been identified. The secondary structure elements have been colored to emphasize the general structural similarity between the two proteins. 

X2 consists of 7 concatenated domains (Fig 2C). The most N-terminal domain (residues 1 to 385, Fig2E) is the guanylyltransferase positioned directly on the XI shell. The guanylyltransferase is cup shaped, and five such domains form a ring about the icosahedral 5-fold axis. The interior of the cup contains the active site and lysines 190 and 171, which are necessary for guanylyl transfer The reovirus guanylyltransferase domain consitutes a novel fold and bears no structural resemblance to the PBCV-1 guanylyltransferase, for which a structure has been determined recently. ... 

The various active sites are ordered vertically in the core. The transcription complex is tethered inside the X,1 shell and below the X2 turret the guanylyltransferase active sites are at the base of the turret and one set of methyltransferase active sites is half way up, and another set is at the top of the turret. There is no biochemical evidence to establish which methyltransferase domain is the 7N and which is the 2 0 methylase. One possibility is that the vertical ordering of the active sites reflects the temporal ordering of the reactions, so that since 7N methyltransfer always precedes 2 0 methyltransfer, the methyltransferase near the middle of the turret methylates 7N and the methyltransferase near the top of the turret methylates the 2 0. Probably such a vertical ordering alone would not impose an order on the methylation reactions, and it seems likely that the reovirus 2 0 methyltransferase, like VP39 from vaccinia, only methylates a cap structure that has been methylated previously at the 5 guanosine moiety. 

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