title: Single-molecule force spectroscopic studies on intra- and intermolecular interactions of G-quadruplex aptamer with target Shp2 protein.
abstract: With widespread applications in biosensors, diagnostics, and therapeutics, much investigation has been made in the structure of the G-quadruplexes and mechanism of their interactions with protein targets. However, in view of AFM based single-molecule force spectroscopic (SMFS) studies of G-quadruplex systems, only bimolecular approaches have been employed. In this article, we present an improved dual-labeling approach for surface immobilization of G-quadruplex DNA apatmers for investigation of intramolecular interaction from an integral unimolecular G-quadruplex system. The melting force of HJ24 G-quadruplex aptamer in the presence of K(+) has been successfully measured. It has been found that dynamic equilibrium exists between unfolding and folding structures of the HJ24 aptamer even in pure water. We also investigated the interactions between the HJ24 aptamer and its target protein (Shp2) under the same solution condition. The HJ24/Shp2 unbinding force in the absence of K(+), 42.0 pN, is about 50% smaller than that in the presence of K(+), 61.7 pN. The great reduction in force in the absence of K(+) suggests that the stability of G-quadruplex secondary structure is important for a stable HJ24/Shp2 binding. The methodology developed and demonstrated in this work is applicable for studying the stability of secondary structures of other unimolecular G-quadruplex aptamers and their interactions with target proteins.
authors.affiliation: State Key Laboratory of Physical Chemistry of the Solid Surfaces, Department of Chemistry, Department of Chemical Biology, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, PR China.
authors.forename: Xue-Qin
authors.initials: XQ
authors.lastname: Zhao
authors.forename: Jie
authors.initials: J
authors.lastname: Wu
authors.forename: Jing-Hong
authors.initials: JH
authors.lastname: Liang
authors.forename: Jia-Wei
authors.initials: JW
authors.lastname: Yan
authors.forename: Zhi
authors.initials: Z
authors.lastname: Zhu
authors.forename: Chaoyong James
authors.initials: CJ
authors.lastname: Yang
authors.forename: Bing-Wei
authors.initials: BW
authors.lastname: Mao
mesh_terms: D000818:Animals; D052157:Aptamers, Nucleotide / Q000737:chemistry / Q000378:metabolism*; D001483:Base Sequence; D054856:G-Quadruplexes; D006801:Humans; D018625:Microscopy, Atomic Force / Q000379:methods*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011188:Potassium / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11 / Q000737:chemistry / Q000378:metabolism*; D013499:Surface Properties
chemical_list: D052157:Aptamers, Nucleotide; C558493:HJ24 aptamer; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D011188:Potassium