title: Kinetics study on the HIV-1 ectodomain protein quaternary structure formation reveals coupling of chain folding and self-assembly in the refolding cascade.
abstract: Entry of HIV-1 into the target cell is mediated by the envelope glycoprotein consisting of noncovalently associated surface subunit gp120 and transmembrane subunit gp41. To form a functional gp41 complex, the protein undergoes hairpin formation and self-assembly. The fusion event can be inhibited by gp41-derived peptides at nanomolar concentration and is highly dependent on the time of addition, implying a role of folding kinetics on the inhibitory action. Oligomerization of the gp41 ectodomain was demonstrated by light scattering measurements. Kinetic study by stopped-flow fluorescence and absorption measurements (i) revealed a multistate folding pathway and stable intermediates; (ii) showed a dissection of fast and slow components for early and late stages of folding, respectively, with 3 orders of magnitude difference in the time scale; (iii) showed the slow process was attributed to misfolding and unzipping of the hairpin; and (iv) showed retardation of the native hairpin formation is assumed to lead to coupling of the correctly registered hairpin and self-assembly. This coupling allows the deduction on the time scale of intrachain folding (0.1-1 s) for the protein. The folding reaction was illustrated by a free energy profile to explain the temporal dichotomy of fast and slow steps of folding as well as effective inhibition by gp41-derived peptide.
authors.affiliation: Institute of Chemistry, Academia Sinica , Taipei, Taiwan, Republic of China 11529.
authors.forename: Shu-Fang
authors.initials: SF
authors.lastname: Cheng
authors.forename: Tai-Ching
authors.initials: TC
authors.lastname: Sung
authors.forename: Chung-Chieh
authors.initials: CC
authors.lastname: Chang
authors.forename: Mei-Ju
authors.initials: MJ
authors.lastname: Chou
authors.forename: Yun-Wei
authors.initials: YW
authors.lastname: Chiang
authors.forename: Ding-Kwo
authors.initials: DK
authors.lastname: Chang
mesh_terms: D019943:Amino Acid Substitution; D004578:Electron Spin Resonance Spectroscopy; D015699:HIV Envelope Protein gp120 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015700:HIV Envelope Protein gp41 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015497:HIV-1 / Q000378:metabolism*; D007700:Kinetics; D008027:Light; D058849:Protein Refolding; D020836:Protein Structure, Quaternary; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D012235:Rhodamines / Q000737:chemistry; D012542:Scattering, Radiation
chemical_list: D015699:HIV Envelope Protein gp120; D015700:HIV Envelope Protein gp41; D011994:Recombinant Proteins; D012235:Rhodamines