Structures of HIV-1 reverse transcriptase with pre- and post-translocation AZTMP-terminated DNA

Area of Science:

• Biochemistry
• Structural Biology
• Virology

Background:

• HIV-1 reverse transcriptase (RT) is a key target for antiretroviral therapy.
• Azidothymidine (AZT) resistance is a significant clinical challenge, often mediated by enhanced excision of AZT monophosphate (AZTMP).
• Understanding the structural basis of AZT resistance and RT translocation is crucial for developing new therapies.

Purpose of the Study:

• To elucidate the structural mechanisms underlying AZT resistance by examining AZTMP excision.
• To investigate the structural differences between pre-translocation (N) and post-translocation (P) complexes of HIV-1 RT.
• To gain insights into the molecular basis of RT translocation.

Main Methods:

• Determined crystal structures of HIV-1 RT in pre-translocation (N) and post-translocation (P) complexes.
• Analyzed structures at 3.0 and 3.1 A resolution.
• Performed docking of a deoxynucleotide triphosphate (dNTP) into the P complex.

Main Results:

• Crystal structures of N and P complexes provide atomic-level detail of AZTMP excision.
• Steric crowding in the P complex upon dNTP binding favors the N complex, the substrate for excision.
• Structural differences between N and P complexes implicate the YMDD loop in the translocation process.

Conclusions:

• The YMDD loop acts as a 'springboard' facilitating primer terminus movement during translocation.
• Structural insights explain enhanced AZTMP excision, a key mechanism of AZT resistance.
• Understanding these mechanisms can guide the design of novel HIV-1 RT inhibitors.