Cryoelectron microscopic examination of human immunodeficiency virus type 1 virions with mutations in the cyclophilin...

The human immunodeficiency virus type 1 capsid protein contains a conserved P217X4PX2PX5P231 motif. Mutation at Pro-222 decreases virion incorporation of cyclophilin A, while mutation at Pro-231 abolishes infectivity. Although viral RNA incorporation and protease cleavage of the Gag precursor were not affected by these mutations, cryoelectron microscopy revealed a loss of virion maturation in P231A particles.