of about 70 serologically related viruses (Castro, Ayala, Ramos-Castaneda, Ortega, Tapia-Ramirez et al., 1004, p. 211). There are actually four known dengue virus serotypes (dengue-1, dengue-2, dengue-3, and dengue-4). Mature dengue virions consist of "a single-stranded RNA genome surrounded by an approximately icosahedral or isometric nucleocapsid about 30 nanometers in diameter" (Henchal & Putnak, 1990, pp. 376-396). The nucleocapsid is coated by a lipid envelope of about 10 nanometers in diameter, thus giving a virus particle which is roughly 50 nanometers in diameter.
The dengue RNA has positive-strand polarity and can be translated in vitro. Moreover, the 5' end of the RNA is capped, however there is no poly (A) tail at the 3' end (Castro et al., 1004, p. 211). This RNA encodes various structural and nonstructural viral proteins.
The mature dengue virion is comprised of the following three structural proteins: (1) the C protein (i.e., the nucleocapsid or core protein; (2) the M protein (i.e., the membrane-associated protein; and (3) the E protein (i.e., the envelope protein). In addition, immature virus may also contain prM or "precursor of M" proteins (Henchal & Putnak, 1990, pp. 376-396). The C protein is highly basic. This gives it the ability to interact with the virion RNA. In contrast, the E protein possesses functional domains that enable it to, for example, interact with certain cell surface receptors. The exact function of the M protein remains unknown.
The genes that encode the dengue virus structural proteins occur at the RNA strand's 5' end, and make up just over a quarter of the entire genome. These genes are in the following order: C, prM(M), and E. Translational mechanisms typically produce
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