Background: The O. tesota lectin PF2 is a tetrameric protein with subunits of 33 kDa
that recognizes only complex carbohydrates, resistant to proteolytic enzymes and has insecticidal
activity against Phaseolus beans pest.
Objective: To explore PF2 lectin features at different protein structural levels and to evaluate the effect
of temperature and pH on its functionality and conformational stability.
Methods: PF2 lectin was purified by affinity chromatography. Its primary structure was resolved
by mass spectrometry and analyzed by bioinformatic tools, including its tertiary structure homology
modeling. The effect of temperature and pH on its conformational traits and stability was addressed
by dynamic light scattering, circular dichroism, and intrinsic fluorescence. The hemagglutinating
activity was evaluated using a suspension of peripheral blood erythrocytes.
Results: The proposed PF2 folding comprises a high content of beta sheets. At pH 7 and 25°C, the
hydrodynamic diameter (Dh) was found to be 12.3 nm which corresponds to the oligomeric native
state of PF2 lectin. Dh increased under the other evaluated pH and temperature conditions, suggesting
protein aggregation. At basic pH, PF2 exhibited low conformational stability. The native PF2
(pH 7) retained its full hemagglutinating activity up to 45°C and exhibited one transition state with
a melting temperature of 76.8°C.
Conclusion: PF2 showed distinctive characteristics found in legume lectins. The pH influences the
functionality and conformational stability of the protein. PF2 lectin displayed a relatively narrow
thermostability to the loss of secondary structure and hemagglutinating activity.
Keywords: Circular dichroism, dynamic light scattering, hemagglutination, homology modeling, intrinsic fluorescence, PF2
lectin, pH, thermostability.
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