Distinct mechanisms of lipid bilayer perturbation induced by peptides derived from the membrane-proximal external region of HIV-1 gp41
Biochemistry 48(23) : 5320-5331 (2009)
Laburpena
The conserved, membrane-proximal external region (MPER) of the human immunodeficiency
virus type-1 envelope glycoprotein 41 subunit is required for fusogenic activity. It has been proposed that
MPER functions by disrupting the virion membrane. Supporting its critical role in viral entry as a membranebound
entity, MPER constitutes the target for broadly neutralizing antibodies that have evolved mechanisms
to recognize membrane-inserted epitopes. We have analyzed here the molecular mechanisms of membrane
permeabilization induced by N-preTM and PreTM-C, two peptides derived from MPERsequences showing a
tendency to associate with the bilayer interface or to transfer into the hydrocarbon core, respectively. Both
peptides contained the full epitope sequence recognized by the 4E10 monoclonal antibody (MAb4E10), which
was subsequently used to probe peptide accessibility from the water phase. Capacities of N-preTM and
PreTM-C for associating with vesicles and inducing their permeabilization were comparable. However,
MAb4E10 specifically blocked the permeabilization induced by N-preTM but did not appreciably affect that
induced by PreTM-C. Supporting the existence of different membrane-bound lytic structures, N-preTM
was running as a monomer on SDS-PAGE and induced the graded release of vesicular contents, whereas
PreTM-C migrated on SDS-PAGE as dimers and permeabilized vesicles following an all-or-none mechanism,
reminiscent of that underlying melittin-induced membrane lysis. These results support the functional
segmentation of gp41 membrane regions into hydrophobic subdomains, which might expose neutralizing
epitopes and induce membrane-disrupting effects following distinct patterns during the fusion cascade.