CRYOELECTRON MICROSCOPIC EXAMINATION OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 VIRIONS WITH MUTATIONS IN THE CYCLOPHILIN-A BINDING LOOP

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