Retroviral reverse transcriptase (RT) plays a key role in the early stage of virus life cycle by converting the viral single-stranded RNA genome into a double-stranded DNA.Although the protein crystal structure of full-length moloney murine leukemia virus (MMLV) RT has been determined,details of the ternary complex (includes the RT,template/primer and dNTP) remain elusive,thus the functional contributions of RT,s structural features are largely unknown.On the basis of similarities with human immunodeficiency viruses type l (HIV-1) RT,we modeled template/primer and dNTP substrates into the MMLV RT structures.From these models,we observed that Tyr64,Asp114 and Arg116 in the fingers domain of MMLV RT were three highly important template terminus binding residues,which are essential for HIV-1 RT catalytic function and fidelity.