Hiv-1 gag: Difference between revisions
No edit summary |
Michal Harel (talk | contribs) No edit summary |
||
| Line 2: | Line 2: | ||
==HIV-1 Gag== | ==HIV-1 Gag== | ||
The HIV-1 Gag protein is the major structural protein required for virus assembly. It is synthesized as a polyprotein in the cytosol of an infected cell, and contains four functional segments; MA, CA (NTD and CTD), NC, and p6. The NC region is flanked by two "spacer" segments, denoted SP1 and SP2. The polyprotein is all alpha helical, except the NC region, which is composed of two RNA interacting zinc knuckle domains. Gag is often referred to as an "assembly machine" because expression of Gag alone is sufficient to produce budding virus-like particles (VLP's), due to multimerization of roughly 2000 Gag molecules per virion. Here, we will take a closer look at the MA, CA, and NC domains, and how the structural components of these domains aid in the assembly of virus particles. Viral particles can be classified as immature (pre-budding and non-infectious), and mature (post-budding and infectious), and this exchange is mediated by the HIV-1 protease. Upon viral budding, Gag is cleaved by the HIV-1 protease at multiple sites, thus possibly changing many of the structural interactions that make up the "immature" particle. For simplicity, we will only be discussing the immature formation of Gag on the plasma membrane of infected cells, as it coordinates organized viral budding. Also, it is thought that Gag forms a hexamer structure (deduced from electron microscopy studies) upon virus assembly, but because of the difficulties encountered by attempting to crystallize a multimeric structure, the exact formation of the hexamer is still up for debate. Current models predict that the MA and CA domains interact to form trimers, and these trimers conglomerate and display hexagonal symmetry. | The '''HIV-1 Gag''' protein is the major structural protein required for virus assembly. It is synthesized as a polyprotein in the cytosol of an infected cell, and contains four functional segments; MA, CA (NTD and CTD), NC, and p6. The NC region is flanked by two "spacer" segments, denoted SP1 and SP2. The polyprotein is all alpha helical, except the NC region, which is composed of two RNA interacting zinc knuckle domains. Gag is often referred to as an "assembly machine" because expression of Gag alone is sufficient to produce budding virus-like particles (VLP's), due to multimerization of roughly 2000 Gag molecules per virion. Here, we will take a closer look at the MA, CA, and NC domains, and how the structural components of these domains aid in the assembly of virus particles. Viral particles can be classified as immature (pre-budding and non-infectious), and mature (post-budding and infectious), and this exchange is mediated by the HIV-1 protease. Upon viral budding, Gag is cleaved by the HIV-1 protease at multiple sites, thus possibly changing many of the structural interactions that make up the "immature" particle. For simplicity, we will only be discussing the immature formation of Gag on the plasma membrane of infected cells, as it coordinates organized viral budding. Also, it is thought that Gag forms a hexamer structure (deduced from electron microscopy studies) upon virus assembly, but because of the difficulties encountered by attempting to crystallize a multimeric structure, the exact formation of the hexamer is still up for debate. Current models predict that the MA and CA domains interact to form trimers, and these trimers conglomerate and display hexagonal symmetry. | ||