3ZH2

Structure of Plasmodium falciparum lactate dehydrogenase in complex with a DNA aptamer

Summary for 3ZH2

• Entry DOI: 10.2210/pdb3zh2/pdb
• Descriptor: L-LACTATE DEHYDROGENASE, DNA APTAMER (3 entities in total)
• Functional Keywords: oxidoreductase
• Biological source: PLASMODIUM FALCIPARUM; More
• Total number of polymer chains: 6
• Total formula weight: 158112.68

Authors

Cheung, Y.W.,Kwok, J.,Law, A.W.L.,Watt, R.M.,Kotaka, M.,Tanner, J.A. (deposition date: 2012-12-20, release date: 2013-09-25, Last modification date: 2023-12-20)

Primary citation

Cheung, Y.W.,Kwok, J.,Law, A.W.L.,Watt, R.M.,Kotaka, M.,Tanner, J.A.
Structural Basis for Discriminatory Recognition of Plasmodium Lactate Dehydrogenase by a DNA Aptamer
Proc.Natl.Acad.Sci.USA, 110:15967-, 2013

PubMed Abstract: DNA aptamers have significant potential as diagnostic and therapeutic agents, but the paucity of DNA aptamer-target structures limits understanding of their molecular binding mechanisms. Here, we report a distorted hairpin structure of a DNA aptamer in complex with an important diagnostic target for malaria: Plasmodium falciparum lactate dehydrogenase (PfLDH). Aptamers selected from a DNA library were highly specific and discriminatory for Plasmodium as opposed to human lactate dehydrogenase because of a counterselection strategy used during selection. Isothermal titration calorimetry revealed aptamer binding to PfLDH with a dissociation constant of 42 nM and 2:1 protein:aptamer molar stoichiometry. Dissociation constants derived from electrophoretic mobility shift assays and surface plasmon resonance experiments were consistent. The aptamer:protein complex crystal structure was solved at 2.1-Å resolution, revealing two aptamers bind per PfLDH tetramer. The aptamers showed a unique distorted hairpin structure in complex with PfLDH, displaying a Watson-Crick base-paired stem together with two distinct loops each with one base flipped out by specific interactions with PfLDH. Aptamer binding specificity is dictated by extensive interactions of one of the aptamer loops with a PfLDH loop that is absent in human lactate dehydrogenase. We conjugated the aptamer to gold nanoparticles and demonstrated specificity of colorimetric detection of PfLDH over human lactate dehydrogenase. This unique distorted hairpin aptamer complex provides a perspective on aptamer-mediated molecular recognition and may guide rational design of better aptamers for malaria diagnostics.

PubMed: 24043813
DOI: 10.1073/PNAS.1309538110

Experimental method

X-RAY DIFFRACTION (2.1 Å)