Fig. 5: Binding kinetics analysis discloses distinct impact on RBD/hACE2 association and dissociation kinetics by CR2 and CR3 subdomains respectively. | Communications Biology

Fig. 5: Binding kinetics analysis discloses distinct impact on RBD/hACE2 association and dissociation kinetics by CR2 and CR3 subdomains respectively.

From: Interfacial subregions of SARS-CoV-2 spike RBD to hACE2 affect intermolecular affinity by their distinct roles played in association and dissociation kinetics

Fig. 5

A Association kinetics profiles of RBD/hACE2 complex formation by SARS-CoV-2 chimeric mutants of swapped CR1/2/3 and single residue mutants reveal significant CR2’s impact on RBD/hACE2’s initial contact with hACE2, in which long range electrostatic force are involved. The mutations’ impact as compared to WT SARS-CoV-2 RBD was quantified as the ratio of ka(RBD mutant) to ka(wild type). For the swapped CR2 mutants from SARS-CoV-1 and Omicron (B.1.1.529 & BA.5.2), the mutated residues are marked and positively charged residues are labeled in orange. B Dissociation kinetics of RBD/hACE2 complex formation by SARS-CoV-2 chimeric mutants of swapped CR1/2/3 and single key residue mutants reveal CR3’s significant impact on RBD/ hACE2 complex stability. The mutations’ impact as compared to WT SARS-CoV-2 RBD was quantified as the ratio of kd(wild type) to kd(RBD mutant). C Relative binding affinity change due to swapped CR1/2/3 subdomains or single key residue mutations as compared to WT SARS-CoV-2 RBD interacting with hACE2. The mutations’ impact is quantitatively compared by ratio of KD(wild type) to KD(RBD mutant). D Based on the kinetics data in A, spike RBD surface potential map of swapped CR2 mutants from SARS-CoV-1 and Omicron (B.1.1.529 & BA.5.2) as compared to that of WT spike RBD suggests that the long range Coulombic electrostatic forces alter the spike RBD/hACE2 association kinetics. Below each subgraph, the range of surface potential distribution is labeled. The hACE2-contact surfaces of spike RBD’s CR1, CR2 and CR3 subregions are outlined with purple, red and green dash lines respectively. For all CR1/2/3 swapped mutants and single mutants, histograms reflecting binding kinetics are presented in purple, red and yellow respectively, while those of native RBDs of SARS-CoV-1/2 and subvariants are colored in dark grey. All error bars represent standard deviations resulting from ka, kd, and KD values obtained through three or more independent experiments.

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