jp312845w_si_001.pdf (96.93 kB)
Solid-State Nuclear Magnetic Resonance Measurements of HIV Fusion Peptide 13CO to Lipid 31P Proximities Support Similar Partially Inserted Membrane Locations of the α Helical and β Sheet Peptide Structures
journal contribution
posted on 2016-02-18, 18:28 authored by Charles
M. Gabrys, Wei Qiang, Yan Sun, Li Xie, Scott D. Schmick, David P. WelikyFusion
of the human immunodeficiency virus (HIV) membrane and the
host cell membrane is an initial step of infection of the host cell.
Fusion is catalyzed by gp41, which is an integral membrane protein
of HIV. The fusion peptide (FP) is the ∼25 N-terminal residues
of gp41 and is a domain of gp41 that plays a key role in fusion catalysis
likely through interaction with the host cell membrane. Much of our
understanding of the FP domain has been accomplished with studies
of “HFP”, i.e., a ∼25-residue peptide composed
of the FP sequence but lacking the rest of gp41. HFP catalyzes fusion
between membrane vesicles and serves as a model system to understand
fusion catalysis. HFP binds to membranes and the membrane location
of HFP is likely a significant determinant of fusion catalysis perhaps
because the consequent membrane perturbation reduces the fusion activation
energy. In the present study, many HFPs were synthesized and differed
in the residue position that was 13CO backbone labeled.
Samples were then prepared that each contained a singly 13CO labeled HFP incorporated into membranes that lacked cholesterol.
HFP had distinct molecular populations with either α helical
or oligomeric β sheet structure. Proximity between the HFP 13CO nuclei and 31P nuclei in the membrane headgroups
was probed by solid-state NMR (SSNMR) rotational-echo double-resonance
(REDOR) measurements. For many samples, there were distinct 13CO shifts for the α helical and β sheet structures so
that the proximities to 31P nuclei could be determined
for each structure. Data from several differently labeled HFPs were
then incorporated into a membrane location model for the particular
structure. In addition to the 13CO labeled residue position,
the HFPs also differed in sequence and/or chemical structure. “HFPmn”
was a linear peptide that contained the 23 N-terminal residues of
gp41. “HFPmn_V2E” contained the V2E mutation that for
HIV leads to greatly reduced extent of fusion and infection. The present
study shows that HFPmn_V2E induces much less vesicle fusion than HFPmn.
“HFPtr” contained three strands with HFPmn sequence
that were chemically cross-linked near their C-termini. HFPtr mimics
the trimeric topology of gp41 and induces much more rapid and extensive
vesicle fusion than HFPmn. For HFPmn and HFPtr, well-resolved α
and β peaks were observed for A6-, L9-, and L12-labeled samples.
For each of these samples, there were similar HFP 13CO
to lipid 31P proximities in the α and β structures,
which evidenced comparable membrane locations of the HFP in either
structure including insertion into a single membrane leaflet. The
data were also consistent with deeper insertion of HFPtr relative
to HFPmn in both the α and β structures. The results supported
a strong correlation between the membrane insertion depth of the HFP
and its fusogenicity. More generally, the results supported membrane
location of the HFP as an important determinant of its fusogenicity.
The deep insertion of HFPtr in both the α and β structures
provides the most relevant membrane location of the FP for HIV gp41-catalyzed
membrane fusion because HIV gp41 is natively trimeric. Well-resolved
α and β signals were observed in the HFPmn_V2E samples
with L9- and L12- but not A6-labeling. The α signals were much
more dominant for L9- and L12-labeled HFPmn_V2E than the corresponding
HFPmn or HFPtr. The structural model for the less fusogenic HFPmn_V2E
includes a shorter helix and less membrane insertion than either HFPmn
or HFPtr. This greater helical population and different helical structure
and membrane location could result in less membrane perturbation and
lower fusogenicity of HFPmn_V2E and suggest that the β sheet
fusion peptide is the most functionally relevant structure of HFPmn,
HFPtr, and gp41.
History
Usage metrics
Categories
Keywords
gp 41. HFP catalyzes fusionHFPtrresidue positionmembrane locationHIV gp 4113 CO shiftsgp 41HFPmnintegral membrane proteinβ sheet fusion peptidemembrane insertion deptholigomeric β sheet structurehost cell membraneHFP 13 CO nucleifusion catalysisREDORSSNMRβ sheet structuresβ Sheet Peptide StructuresFusionPartially Inserted Membrane Locationsfusion activation energyNMRvesicle fusionHIV Fusion Peptide 13 CO13 CO backbonemembrane location modellipid 31 P proximitiesmembrane perturbationα helical31 P nuclei13 COHFP 13 COV 2E mutationβ structuresLipid 31 P Proximities Support
Licence
Exports
RefWorks
BibTeX
Ref. manager
Endnote
DataCite
NLM
DC