HIV-1 Vpu Protein Forms Stable Oligomers in Aqueous Solution via Its Transmembrane Domain Self-Association

Authors

Saman Majeed
Lan Dang
Md Majharul Islam
Olamide Ishola
Peter P Borbat
Steven J Ludtke
Elka R Georgieva

Publication Date

9-6-2023

Journal

Scientific Reports

DOI

10.1038/s41598-023-41873-0

PMID

37673923

PMCID

PMC10483038

PubMedCentral® Posted Date

9-6-2023

PubMedCentral® Full Text Version

Post-print

Published Open-Access

yes

Keywords

Humans, Chromatography, Gel, Cryoelectron Microscopy, Ear Auricle, HIV Seropositivity, HIV-1, Biochemistry, Biophysics, Biotechnology, Chemical biology, Molecular biology, Structural biology

Abstract

We report our findings on the assembly of the HIV-1 protein Vpu into soluble oligomers. Vpu is a key HIV-1 protein. It has been considered exclusively a single-pass membrane protein. Previous observations show that this protein forms stable oligomers in aqueous solution, but details about these oligomers still remain obscure. This is an interesting and rather unique observation, as the number of proteins transitioning between soluble and membrane embedded states is limited. In this study we made use of protein engineering, size exclusion chromatography, cryoEM and electron paramagnetic resonance (EPR) spectroscopy to better elucidate the nature of the soluble oligomers. We found that Vpu oligomerizes via its N-terminal transmembrane domain (TM). CryoEM suggests that the oligomeric state most likely is a hexamer/heptamer equilibrium. Both cryoEM and EPR suggest that, within the oligomer, the distal C-terminal region of Vpu is highly flexible. Our observations are consistent with both the concept of specific interactions among TM helices or the core of the oligomers being stabilized by hydrophobic forces. While this study does not resolve all of the questions about Vpu oligomers or their functional role in HIV-1 it provides new fundamental information about the size and nature of the oligomeric interactions.

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