Microsecond dynamics control the HIV-1 envelope conformation.

Area of Science:

• Structural biology
• Virology
• Biophysics

Background:

• The Human Immunodeficiency Virus type 1 (HIV-1) Envelope (Env) glycoprotein mediates viral entry by undergoing significant conformational changes upon receptor binding.
• Understanding the dynamic structural transitions of Env is crucial for developing effective vaccines and therapeutics.
• Previous studies have characterized millisecond-timescale events, but faster microsecond-timescale dynamics remain largely unexplored.

Approach:

• Utilized time-resolved, temperature-jump small-angle X-ray scattering (TR-TJ-SAXS) to probe structural rearrangements of an HIV-1 Env ectodomain construct.
• Achieved microsecond precision to capture rapid dynamic events previously inaccessible.
• Employed model fitting to interpret observed structural transitions.

Key Points:

• Detected two distinct structural transitions in the microsecond timescale preceding Env opening.
• Identified an early, rapid order-to-disorder transition in trimer apex loop contacts.
• Demonstrated that this early transition may bypass conventional allosteric locking mechanisms.

Conclusions:

• The rapid dynamics of the HIV-1 Env ectodomain, particularly in the trimer apex loop, represent a critical intermediate state.
• Engineered an Env construct to stabilize apex loop contacts, altering antibody binding orientation.
• Blocking these early intermediate states offers a promising strategy for eliciting broadly neutralizing antibodies for HIV vaccination.