The biologically active form of HIV-1 RT is a heterodimer consisting of two subunits, p66 (66 kDa) and p51 (51 kDa). The p51 subunit is derived from p66 by proteolytic cleavage of its Cterminal domain [3] . The polymerase domain of p66 and p51, resembling a right hand configuration, consists of four subdomains, which are known as fingers, palm, thumb and connection. The fingers, palm and thumb subdomains of p66 form a nucleic acid binding cleft and the connection subdomains of the two subunits form the floor of the nucleic acid binding site [4] [5] [6] [7] .