Relating the Structure of HIV-1 Reverse Transcriptase to Its Processing Step.

Area of Science:

• Biophysics
• Enzymology
• Molecular Biology

Background:

• Reverse transcriptase (RT) is crucial for viral replication and DNA synthesis.
• Understanding RT's dynamic motions is key to its enzymatic function, including polymerization and RNase H activity.
• Previous studies have focused on static structures, with less emphasis on dynamic conformational changes during substrate processing.

Purpose of the Study:

• To investigate the normal modes of motion in reverse transcriptase using a coarse-grained model.
• To correlate specific motions with the enzyme's catalytic steps: polymerization and Ribonuclease H (RNase H) activity.
• To elucidate the role of different subunits (p66 and p51) in facilitating these motions.

Main Methods:

• Coarse-grained modeling of the enzyme, utilizing only alpha-carbon positions.
• Calculation of normal modes of motion to identify low-frequency vibrational modes.
• Analysis of the slowest modes to infer their functional relevance in enzymatic processing.

Main Results:

• The slowest normal mode involves hinge bending between the polymerase and RNase H active sites, facilitating RNA strand transfer.
• A clamp-like motion, opening and closing the protein, aids in nucleic acid release and stepwise progression.
• The p51 subunit acts as a scaffold, supporting the dynamic motions of the p66 subunit.
• The p66 subunit exhibits distinct motions, including hinge bending and rotation, essential for substrate processing.

Conclusions:

• Enzyme dynamics, particularly slow normal modes, are critical for the coordinated steps of reverse transcriptase activity.
• Hinge bending and clamp-like motions facilitate the transfer and processing of nucleic acid strands.
• The p51 subunit's role is primarily structural, supporting the functional dynamics of the p66 subunit during enzymatic catalysis.