Crystal structure of SIV matrix antigen and implications for virus assembly.
Rao, Zihe; Belyaev, Alexander S.; Fry, Elizabeth; Roy, Polly; Jones, Ian M.; Stuart, David I.
[Letter] Nature. 378(6558):743-747, December 14, 1995.

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SIMIAN immunodeficiency virus (SIV) is closely related to human immunodeficiency virus (HIV) *RF 1*, their matrix antigens (MAs) sharing some 50% sequence identity. MA is a component of Pr55Gag, the sole protein required for assembly of the virion shell [2]. MA targets Pr55 to the plasma membrane [3], and facilitates incorporation of the virus envelope protein [4] and assembly of the Pr55Gag shell [5]. Cleavage of Pr55 by the viral protease produces the mature protein of relative molecular mass 17-18K, which underlies the host-derived membrane and is important in both virus entry [6] and nuclear localization of the virion core [7]. Here we report the crystal structure of SIV MA. The molecule forms a trimer consistent with oligomerization in vitro [8], the observed virion architecture [9], and various biological properties of MA.

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