Structural Investigation of the HIV-1 Envelope Glycoprotein gp160 Cleavage Site

Abstract

The selective proteolytic activation of the HIV‐1 envelope glycoprotein gp160 by furin and other precursor convertases (PCs) occurs at the carboxyl side of the sequence Arg508‐Glu‐Lys‐Arg511 (site 1), in spite of the presence of another consensus sequence: Lys500‐Ala‐Lys‐Arg503 (site 2). We report on the solution structural analysis of a 19‐residue synthetic peptide, p498, which spans the two gp160‐processing sites 1 and 2, and is properly digested by furin at site 1. A molecular model is obtained for p498, by means of molecular dynamics simulations, from NMR data collected in trifluoroethanol/water. The peptide N‐terminal side presents a 9‐residue helical segment, enclosing the processing site 2; the C‐terminal segment can be described as a loop exposing the processing site 1. A hypothesis for the docking of p498 onto the catalytic domain of human furin, modeled by homology and fitting previous site‐directed mutagenesis studies, is also presented. p498 site 1 is shown to have easy access to the furin catalytic site, unlike the nonphysiological site 2. Finally, on the basis of available data, we suggest a possible structural motif required for the gp160–PCs recognition.

Alterations of pr-M Cleavage and Virus Export in pr-M Junction Chimeric Dengue Viruses

“…The presence of a nearby carbohydrate moiety reduces cleavage efficiency, whereas a polybasic amino acid insertion within the loop or replacement of an uncharged amino acid with a basic residue serves to nullify the adverse influence of the carbohydrate, possibly by reversing the poor accessibility of the target sequence to protease (41,75). For HIV-1 gp160, a loop configuration for the furin cleavage motif was also proposed (60,63). If the dengue virus pr-M junction is located in a similar loop, the P5 deletion in TBEVpr/16681 may shorten or otherwise alter the local conformation of this loop in dengue virus prM in such a way that basic residues at more distal positions cannot compensate for the lack of P5 arginine for efficient cleavage.…”

Domain Flexibility Modulates the Heterogeneous Assembly Mechanism of Anthrax Toxin Protective Antigen

“…1c) has maximized the motif for recognition by a broad number of these furin-type PC enzymes. 38 While NMR techniques have elucidated the structure of a furin cleavage site in a 19-residue peptide from gp160, 53 atomic-resolution structural information for furin cleavage sites in proviral and protoxin proteins have been challenging to obtain, because the sites are typically found on flexible loop structures. To gain an understanding on the structural basis of toxin assembly and furin activation we crystallized a variant of anthrax toxin PA and solved its structure to 1.45-Å resolution.…”

Heparin enhances the furin cleavage of HIV‐1 gp160 peptides

“…The lack of processing at site2 may be rationalized on the basis of structural motifs. In fact, the 19mer NMR molecular model in TFE revealed that site2 is embedded in a helical segment, whereas site1 is in a exposed loop at the C-terminus of the peptide [12]. In contrast, the 41mer and 51mer, spanning extensive sequence of the gp160 cleavage region, were shown to represent very poor furin substrates.…”

“…The exact role of site2 is unknown, though mutations of gp160 KAKR 503 sequence result in an unprocessed precursor [11]. Conformational differences between site1 and site2 may explain the preference of furin for site1 [12].…”