THE STRUCTURE OF ALFALFA MOSAIC-VIRUS CAPSID PROTEIN ASSEMBLED AS A T=1 ICOSAHEDRAL PARTICLE AT 4.0-ANGSTROM RESOLUTION

K. Fukuyama, S, S, Abdel-Meguid, J, E, Johnson, and M. G, Rossmann (J, Mol, Biol, 167:873-984, 1983) reported the structure of alfalfa mosai c virus assembled from the capsid protein as a T=1 icosahedral empty p article at 4.5-Angstrom resolution, The information contained in the s tructure included the particle size, protein shell thickness, presence of wide holes at the icosahedral fivefold axes, and a proposal that t he capsid protein adopts a P-barrel structure, In the present work, th e X-ray diffraction data of Fukuyama et al, as well as the data subseq uently collected by I, Fita, P. Hata, and M. G, Rossmann (unpublished) were reprocessed to 4.0-Angstrom resolution, and the structure was so lved by molecular replacement, The current structure allowed the traci ng of the polypeptide chain of the capsid protein confirming the beta- sandwich fold and provides information on intersubunit interactions in the particle. However, it was not possible to definitively assign the amino acid sequence to the side chain density at 4-Angstrom resolutio n, The particle structure was also determined by cryoelectron microsco py and image reconstruction methods and found to be in excellent agree ment with the X-ray model.