title: G-quadruplex DNA aptamers generated for systemin.
abstract: Ligands specific to bioactive molecules play important roles in biomedical researches and applications, such as biological assay, diagnosis and therapy. Systemin is a peptide hormone firstly identified in plant. In this paper we report the selection of a group of DNA aptamers that can specifically bind to systemin. Through comparing the predicted secondary structures of all the aptamers, a hairpin structure with G-rich loop was determined to be the binding motif of these aptamers. The G-rich loop region of this binding motif was further characterized to fold into an antiparallel G-quadruplex by truncation-mutation assay and CD spectrum. The apparent equilibrium dissociation constant (K(d)) of one strong binding sequence (S-5-1) was measured to be 0.5 μM. The specificity assay shows that S-5-1 strongly bind to whole systemin, weakly bind to truncated or mutated systemin and does not bind to the scrambled peptide with the same amino acid composition as systemin. The high affinity and specificity make S-5-1 hold potentials to serve as a molecular ligand applied in detection, separation and functional investigation of systemin in plants.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Bing
authors.forename: Tianjun
authors.initials: T
authors.lastname: Chang
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Yang
authors.forename: Hongcheng
authors.initials: H
authors.lastname: Mei
authors.forename: Xiangjun
authors.initials: X
authors.lastname: Liu
authors.forename: Dihua
authors.initials: D
authors.lastname: Shangguan
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry* / Q000378:metabolism*; D001667:Binding, Competitive; D054856:G-Quadruplexes; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D009994:Osmolar Concentration; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*
chemical_list: D052157:Aptamers, Nucleotide; D008024:Ligands; D010455:Peptides; C073704:systemin