Chemistry of conjugation to gold nanoparticles affects G-protein activity differently

Abstract

BackgroundGold nanoparticles (AuNP) are extensively used as biophysical tools in the area of medicine and technology due to their distinct properties. However, vivid understanding of the consequences of biomolecule-nanomaterial interactions is still lacking. In this context, we explore the affect of conjugation of Gαi1 subunit (of heterotrimeric G-proteins) to AuNP and examine its consequences. We consider two bio-conjugation strategies covalent and non-covalent binding.ResultsAffinity of the AuNP to the Gαi1 is 7.58 × 10 12 M-1. AuNP conjugated Gαi1 exhibits altered kinetics of activation, non-covalent bio-conjugates displays retarded kinetics, up to 0.88 fold when GTPγS was used as ligand, of protein activation contrary to covalent conjugates which accelerates it to ~ 5 fold. Conjugation influence intrinsic Gαi1 GTPase function in conflicting modes. Non-covalent conjugation inhibits GTPase function (decrease in activity upto 0.8 fold) whilst covalent conjugation drastically accelerates it (12 fold increase in activity). Altered basal nucleotide uptake in both types of conjugates and GTPase function in non-covalent conjugate are almost comparable except for GTPase property of covalent conjugate. The effect is despite the fact that conjugation does not change global conformation of the protein.ConclusionThese findings provide clear evidence that nanoparticles, in addition to ‘passive interaction’ with protein (biomolecule), can interact “actively” with biomolecule and modify its function. This concept should be considered while engineering nanoparticle based delivery systems in medicine.

Recombinant Interleukin-1 Receptor Antagonist Conjugated to Superparamagnetic Iron Oxide Nanoparticles for Theranostic Targeting of Experimental Glioblastoma

“…Significantly, magnetic conjugates demonstrated biologic anti-edemal therapy at significantly lower concentrations of receptor antagonist (i.e., 2.5 mg/kg) in comparison to the administration of purified protein (when the effect was detected at concentrations of IL-1Ra exceeding 25 mg/kg). Presumably, covalent binding of protein to the nanoparticles may increase the biologic activity of the protein, probably due to molecular interaction between the nanomaterial and the biomolecule [47] , [48] . Correspondingly, it was shown by Singh et al that conjugation of the Gαi1 subunit (of heterotrimeric G-proteins) to gold nanoparticles accelerated its GTPase activity five-fold [47] .…”

“…Presumably, covalent binding of protein to the nanoparticles may increase the biologic activity of the protein, probably due to molecular interaction between the nanomaterial and the biomolecule [47] , [48] . Correspondingly, it was shown by Singh et al that conjugation of the Gαi1 subunit (of heterotrimeric G-proteins) to gold nanoparticles accelerated its GTPase activity five-fold [47] . In addition, the phenomenon of enhanced permeability and retention allows the magnetic nanoparticles to enter the tumor interstitial space, whereas the suppressed lymphatic filtration allows them to stay there [49] .…”

PEG-coated gold nanoparticles attenuate β-adrenergic receptor-mediated cardiac hypertrophy

“…27 Further, AuNPs could conjugate to G-protein and affect the activity of G-protein. 28 These studies suggest that AuNPs may regulate the expression of β1-AR and its downstream signaling pathway which reflects the activity of β1-AR.…”

Susceptibility of microbial cells to the modified PIP2-binding sequence of gelsolin anchored on the surface of magnetic nanoparticles

“…Attachment-based physicochemical phenomena include ionic and hydrophobic interactions and dative bonding, which engages gold surface conduction electrons. Chemisorption via thiol derivatives can occur by the bifunctional linker carbodiimide (EDC)/active esters (NHS— N -hydroxy-succinimide) or by adapter molecules like avidin and biotin [13, 14]. In the case of a terminal amine group present on the surface, non-covalent (hydrogen bonding, ionic, electrostatic) and covalent (imine, enamine, peptide bond etc.)…”