Organization of Pro and Pol proteins. Schematic representations of the mature Pro and Pol proteins and their precursors are drawn for examples from several retroviruses. The sequences representing the mature proteins PR, RT, and IN are indicated. Rectangles, precursor proteins, with solid vertical lines marking major cleavage sites and thick horizontal bars indicating mature proteins. DTG or DSG and YMDD indicate the conserved active site residues in PR and RT. The RNase H domain of RT is also indicated (ASLV: avian sarcoma leucosis virus, MMTV: murine mammary tumor virus, MLV: murine leukemia virus, and FIV: feline immunodeficiency virus).
