Catalytic Magnesium as a Door Stop for DNA Sliding

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• HIV Reverse Transcriptase (HIV RT) is crucial for synthesizing DNA from an RNA template in HIV replication.
• DNA translocation is a key step where the polymerase moves along the DNA template to accommodate incoming nucleotides.

Purpose of the Study:

• To investigate the role of magnesium ions in regulating DNA translocation by HIV RT.
• To determine the free energy profile and timescale of DNA-protein displacement in the closed state of the HIV RT complex.

Main Methods:

• Utilized Molecular Dynamics (MD) simulations to model the complex dynamics.
• Calculated the free energy profile of DNA translocation.
• Estimated the timescale of relative DNA-protein displacement.

Main Results:

• The presence of catalytic magnesium significantly slows down DNA translocation.
• Removing the magnesium ion accelerates the translocation process considerably.
• The rate of translocation upon magnesium removal is faster than active site reopening for new substrate entry.

Conclusions:

• Magnesium ions act as a regulator of DNA translocation in HIV RT.
• Magnesium stabilizes the DNA in a specific orientation during nucleotide addition.
• Mg2+ release facilitates DNA sliding, promoting efficient substrate acceptance and viral DNA synthesis.