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Crystal structure of SIV matrix antigen and implications for virus assembly
1Laboratory of Molecular Biophysics, Oxford, UK.
Abstract:
Simian immunodeficiency virus (SIV) is closely related to human immunodeficiency virus (HIV), 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. MA targets Pr55 to the plasma membrane, and facilitates incorporation of the virus envelope protein and assembly of the Pr55Gag shell. 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 and nuclear localization of the virion core. Here we report the crystal structure of SIV MA. The molecule forms a trimer consistent with oligomerization in vitro, the observed virion architecture, and various biological properties of MA.
Insights
Simian immunodeficiency virus (SIV) matrix antigen (MA) is crucial for virus assembly and membrane targeting. The crystal structure reveals SIV MA forms trimers, explaining its biological functions.
Area of Science:
- Virology
- Structural Biology
- Molecular Biology
Background:
- Simian immunodeficiency virus (SIV) shares significant sequence identity with human immunodeficiency virus (HIV).
- Matrix antigen (MA) is a key component of the Pr55Gag polyprotein, essential for SIV assembly and virion structure.
- MA plays a critical role in targeting Pr55Gag to the plasma membrane and facilitating viral envelope protein incorporation.
Purpose of the Study:
- To determine the crystal structure of Simian immunodeficiency virus matrix antigen (SIV MA).
- To correlate the structural findings with the known biological functions and oligomerization properties of SIV MA.
Main Methods:
- X-ray crystallography was employed to determine the three-dimensional structure of SIV MA.
- Biophysical techniques were used to assess MA oligomerization in vitro.
Main Results:
- The crystal structure of SIV MA was elucidated, revealing its molecular architecture.
- The structure demonstrated that SIV MA forms a trimeric quaternary structure.
- This trimeric form is consistent with in vitro oligomerization data and virion assembly observations.
Conclusions:
- The trimeric structure of SIV MA provides a molecular basis for its role in virion assembly and membrane targeting.
- Understanding SIV MA structure aids in comprehending lentiviral assembly mechanisms, potentially informing HIV research.