The icosahedral capsid of Herpes Simplex Virus (HSV) type I has a diameter of 1250 _ and consists of 4 different structural shell proteins. To pursue the questions regarding the locations of these proteins and their structural detail, we imaged the wild type and the recombinant baculovirus expressed particle with one of the protein (VP26) missing. The difference map allows us to localize the VP26, a 12kD protein unambiguously on all hexons but not pentons, though both of them are made up of the major capsid proteins, VP5. Furthermore, the improved resolution at 19 _ also resolves the VP26 into a large and a small domain. Based on our structural observation, we have proposed a plausible mechanism of the assembly of VP26 on the capsid. Our hypothesis is that the VP26 prefers to form a hexamer to maintain its protein stability once it is synthesized. Structurally, this hexameric VP26 would fit to hexons and not to pentons. This proposed scheme can be experimentally tested by searching for VP26 hexamers in solution. Our future effort will be to extend the structural resolution beyond 19 _ for the HSV capsid by improving both experimental and computational procedures.
NIH ExPorter
NIH ExPorter