Modulation of human immunodeficiency virus type 1 protease autoprocessing by charge properties of surface residue 69.

Mature, fully active human immunodeficiency virus protease (PR) is liberated from the Gag-Pol precursor via regulated autoprocessing. A chimeric protease precursor, glutathione S-transferase-transframe region (TFR)-PR-FLAG, also undergoes N-terminal autocatalytic maturation when it is expressed in Escherichia coli. Mutation of the surface residue H69 to glutamic acid, but not to several neutral or basic amino acids, impedes protease autoprocessing in bacteria and mammalian cells.

Instructor pilot teaching behavior and student pilot stress in flight training.

The purpose of this study was to investigate the relationship between instructor pilot behavior and student pilot stress. Six instructor pilots and 12 undergraduate pilot training students served as subjects. Two students were assigned to each instructor.