In vitro Selection and Interaction Studies of a DNA Aptamer Targeting Protein A

Area of Science:

• Biochemistry
• Molecular Biology
• Biotechnology

Background:

• Protein A is a significant surface protein found on Staphylococcus aureus.
• Aptamers are valuable tools for molecular recognition and diagnostics.
• Developing specific binders for Protein A is crucial for various applications.

Purpose of the Study:

• To select and characterize a novel DNA aptamer targeting Protein A.
• To investigate the binding characteristics and structural requirements of the aptamer.
• To explore the potential applications of the aptamer in detection and purification.

Main Methods:

• FluMag-SELEX (Fluorescent Magnetic-bead Systematic Evolution of Ligands by EXponential enrichment) for aptamer selection.
• Structural investigations and sequence truncation for functional analysis.
• Surface Plasmon Resonance (SPR), MicroScale Thermophoresis (MST), and fluorescence-based assays for binding analysis.

Main Results:

• A DNA aptamer targeting Protein A was successfully selected.
• The aptamer requires a 5'-end stem-loop structure for effective target binding.
• Affinity constants ranged from low micromolar to submicromolar, improving to nanomolar with avidity.
• The aptamer demonstrated high specificity for both native and recombinant Protein A, not cross-reacting with Protein G or L.
• The aptamer successfully bound Staphylococcus aureus cells presenting Protein A.

Conclusions:

• The developed DNA aptamer is a specific and high-affinity binder for Protein A.
• The aptamer's structural features are critical for its binding capability.
• This aptamer holds promise for applications in Protein A detection, affinity purification, and bacterial cell capture.