InterPro: IPR000936 Alphavirus E2 glycoprotein

Alphaviruses are enveloped RNA viruses that use arthropods such as mosquitoes for transmission to their vertebrate hosts, and include Semliki Forest and Sindbis viruses [1]. Alphaviruses consist of three structural proteins: the core nucleocapsid protein C, and the envelope proteins P62 and E1 ( IPR002548) that associate as a heterodimer. The viral membrane-anchored surface glycoproteins are responsible for receptor recognition and entry into target cells through membrane fusion. The proteolytic maturation of P62 into E2 and E3 ( IPR002533) causes a change in the viral surface. Together the E1, E2, and sometimes E3 glycoprotein "spikes" form an E1/E2 dimer or an E1/E2/E3 trimer, where E2 extends from the centre to the vertices, E1 fills the space between the vertices, and E3, if present, is at the distal end of the spike [2, 3]. Upon exposure of the virus to the acidity of the endosome, E1 dissociates from E2 to form an E1 homotrimer, which is necessary for the fusion step to drive the cellular and viral membranes together [4]. This entry represents the alphaviral E2 glycoprotein. The E2 glycoprotein functions to interact with the nucleocapsid through its cytoplasmic domain, while its ectodomain is responsible for binding a cellular receptor.