To characterize the apparent dimerization of FRLT3-LRR, samples were measured in the AUC at 2 loading concentrations 0.38 and 0.92 OD 280, corresponding to 7.6 and 18.3 μM, respectively. The van Holde – Weischet analysis shows a strong mass action effect with a marked shift to a higher sedimentation coefficient distribution for the higher concentration (Figure 1E). Subsequently, to calculate dissociation constant for the monomer-dimer equilibrium, both concentrations were fitted with finite element solutions of the Lamm equation that models the reversible interaction for a monomer-dimer system (Cao and Demeler, 2008; Demeler et al., 2010). The fit resulted in virtually identical KD values for both fits, averaging 43.3 μM (39.7 – 46.9 μM with 95% confidence intervals). Taken together, these data indicate that when LPHN3-OLF associates with FLRT3-LRR, its weak dimerization is converted in the formation of a 1:1 complex.
