Replication of human immunodeficiency virus 1 (HIV-1) involves conversion of its single-stranded RNA genome to double-stranded DNA, which is integrated into the genome of the host. This conversion is catalyzed by reverse transcriptase (RT), which possesses DNA polymerase and RNase H domains. The available crystal structures suggest that at any given time the RNA/DNA substrate interacts with only one active site of the two domains of HIV-1 RT. Unknown is whether a simultaneous interaction of the substrate with polymerase and RNase H active sites is possible. Therefore, the mechanism of the coordination of the two activities is not fully understood. We performed molecular dynamics simulations to obtain a conformation of the complex in which the unwound RNA/DNA substrate simultaneously interacts with the polymerase and RNase H active sites. When the RNA/DNA hybrid was immobilized at the polymerase active site, RNase H cleavage occurred, experimentally verifying that the substrate can simultaneously interact with both active sites. These findings demonstrate the existence of a transient conformation of the HIV-1 RT substrate complex, which is important for modulating and coordinating the enzymatic activities of HIV-1 RT.

Institute of Biochemistry and Biophysics Polish Academy of Sciences 02 106 Warsaw Poland

Institute of Biophysics Academy of Sciences of the Czech Republic 612 65 Brno Czech Republic Regional Centre of Advanced Technologies and Materials Department of Physical Chemistry Faculty of Science Palacky University Olomouc 77146 Olomouc Czech Republic

Laboratory of Protein Structure International Institute of Molecular and Cell Biology 02 109 Warsaw Poland

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