Multifaceted analyses of the interactions between human heart type fatty acid binding protein and its specific aptamers

Aptamer-protein interaction studies have been mainly confined to dissociation constant (Kd) determination. A combinatorial approach involving limited proteolysis mass spectroscopy, molecular docking and CD studies is reported here to elucidate the specific interactions involved. To generate aptamers specific for human FABP3, SELEX was performed incorporating counter SELEX cycles against control FABPs and GST tag, followed by their characterization by EMSA, CD and SVD analysis. Based on computationally obtained aptamer-protein complex models, the interacting aptamer, and protein residues were predicted and supported by limited proteolysis experiments. Two aptamers N13 and N53 specific for human fatty acid binding protein (FABP3) were isolated with corresponding Kd of 0.0743±0.0142μM and 0.3337±0.1485μM for FABP3 interactions. Both aptamers possess stable B-DNA structures at salt concentration of 100mM and pH range (6–9). The N13 aptamer led interaction involved 3 salt bridges and 2 hydrogen bonds, whereas N53 had 2 salt bridges with 8 hydrogen and 7 hydrophobic interactions. The aptamers generated are the first to be reported against human FABP3. The higher interaction footprint of N53 incited synergistic conformational changes in both N53 and FABP3 during interaction, leading to a decline in binding affinity in comparison to N13 which corroborated to the calculated Kd values. This combinatorial method may be used to retrieve the possible specific binding modes and interaction patterns involved in large aptamer-protein complexes. Thus the method can be exploited to identify the optimum aptamer length for in-depth structure-function studies and its tailored applications. [Display omitted] •Developed two specific aptamers against human heart type fatty acid binding protein.•Aptamer-protein interactions were analyzed by a combinatorial approach.•Aptamer-protein interactions were accompanied by change in their conformations.•Aptamers with low Kd exhibited high ionic interactions.•Aptamers with high Kd exhibit more synergistic conformational change.