FIG 1.

A model representing the binding of dTTP at the polymerase active site of RT prior to nucleotide incorporation. The model was built using structural information from structures 1RTD (20), 2IAJ (77), and 3V4I (78). The three amino acid residues that were mutated in the analysis, Y115, Q151, and M184, are shown in cyan. These residues form part of the polymerase active site that surrounds the bound dTTP (yellow). The coordination environments of the two catalytic Mg²⁺ ions (pink) are represented by dotted lines; a coordinating water molecule is labeled “W”.