Assembly and analysis of conical models for the HIV-1 core

The genome of the human immunodeficiency virus (HIV) is packaged within an unusual conical core particle located-at the center of the infectious virio n. The core is composed of a complex of the NC (nucleocapsid) protein and g enomic RNA, surrounded by a shell of the CA (capsid) protein. A method was developed for assembling cones in vitro using pure recombinant HIV-1 CA-NC fusion proteins and RNA templates. These synthetic cores are capped at both ends and appear similar in size and morphology to authentic viral cores. I t is proposed that both viral and synthetic cores are organized on conical hexagonal Lattices, which by Euler's theorem requires quantization of their cane angles. Electron microscopic analyses revealed that the cone angles o f synthetic cores were indeed quantized into the five allowed angles. The v iral core and most synthetic cones exhibited cone angles of approximately 1 9 degrees (the narrowest of the allowed angles). These observations suggest that the core of HIV is organized on the principles of a fullerene cone, i n analogy to structures recently observed for elemental carbon.