title: The effect of graphene oxide on conformation change, aggregation and cytotoxicity of HIV-1 regulatory protein (Vpr).
abstract: The fragment of viral protein R (Vpr), Vpr13-33, plays an important role in regulating nuclear importing of HIV through ion channel formation with a leucine-zipper-like α-helical conformation. Herein we report an approach to reduce cytotoxicity of Vpr13-33 by graphene oxide induced conformation change and aggregation. Preferential adsorption of Vpr13-33 on graphene oxide accompanied by conformation change from α-helix to β-sheet structures has been observed by using atomic force microscopy (AFM) and circular dichroism (CD). The submolecular structures of the Vpr13-33 peptide assembly on graphite surface have been identified by using scanning tunneling microscopy (STM), which confirms the β-sheet structures of Vpr13-33 on graphene oxide surface. The reduced cytotoxicity of Vpr13-33 to neuroblastoma cells and T cells are detected by MTT assay, which could be associated with the conformation change and stimulated aggregation of Vpr13-33 upon addition of graphene oxide through hydrophobic interaction. Furthermore, fluorescent leakage assay by using large unilamellar vesicles (LUVs) indicated that the GO reduced Vpr13-33-induced cytotoxicity could be associated with the inhibited "pore forming" function of Vpr13-33 by conformation change and aggregation.
authors.affiliation: National Center for Nanoscience and Technology, Beijing 100190, PR China.
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Mao
authors.forename: Chenxuan
authors.initials: C
authors.lastname: Wang
authors.forename: Wenfeng
authors.initials: W
authors.lastname: Zeng
authors.forename: Chunling
authors.initials: C
authors.lastname: Zhang
authors.forename: Zhongjun
authors.initials: Z
authors.lastname: Li
authors.forename: Ying
authors.initials: Y
authors.lastname: Fang
authors.forename: Yanlian
authors.initials: Y
authors.lastname: Yang
authors.forename: Wei
authors.initials: W
authors.lastname: Liang
authors.forename: Chen
authors.initials: C
authors.lastname: Wang
mesh_terms: D002470:Cell Survival / Q000187:drug effects*; D019281:Dimerization; D006108:Graphite / Q000737:chemistry* / Q000633:toxicity*; D053769:Nanocapsules / Q000737:chemistry* / Q000633:toxicity*; D010087:Oxides / Q000737:chemistry / Q000633:toxicity; D011487:Protein Conformation; D054325:vpr Gene Products, Human Immunodeficiency Virus / Q000633:toxicity*
chemical_list: D053769:Nanocapsules; D010087:Oxides; D054325:vpr Gene Products, Human Immunodeficiency Virus; D006108:Graphite