The image was created by Michael F. Summers, Rossitza K. Gitti, Brian M. Lee and Jill Walker, investigators with the Howard Hughes Medical Institute at the University of Maryland Baltimore County, along with a Wesley I. Sundquist and Shanghee Yoo from the University of Utah. In a report in the July 12 issue of Science, the researchers display a detailed picture of the central region of the HIV-1 capsid (CA) proteinthe molecule that makes up the shell containing the RNA and enzymes necessary for HIV-1 to replicate and infect its host. Computer-analyzed magnetic resonance imaging was used to decipher the molecule's complicated structure.
Summers and his collaborators, who have been pursuing the structure of the CA protein for six years, were stunned when they looked at their results. The protein is almost entirely composed of alpha helicesthe dominant corkscrew pattern seen here, in which the amino acids that make up the protein wind into a hollow cylinder shape. The alpha helices are disrupted by two abrupt "beta hairpin turns," or U-turns, as well as by a looplike formation. Such a structure has never before been seen among the proteins that make up the shields surrounding the genetic material in viruses.