Progress in FY2015 was in the following areas: (1) HIV-1 CAPSID ASSEMBLIES. We have obtained quantitative structural constraints for the dimer interface in tubular CA assemblies, using a variety of solid state NMR techniques (BroBaRR, REDOR, NCCN tensor correlation, etc.) Previous studies by crystallography, cryoEM, and solution NMR have resulted in disparate structural models for this critical region of intermolecular association. From our solid state NMR constraints, we have developed a detailed structural model for the dimer interface in the tubular assemblies. This represents the first demonstration that solid state NMR measurements can provide new atomic-level structural information to complement information from cryoEM and crystallography. A paper describing this work is in preparation. We have also examined the R18L mutant of CA, which forms either spherical assemblies or planar 2D lattices under certain assembly conditions. Comparison with solid state NMR spectra of wild-type CA tubes provides new information about variations in local structure (particularly sidechain conformations) and local dynamics in CA spheres, tubes, and planar assemblies. A paper describing this work is in preparation.
