Fig. 3: Impact of CD5L mutants on Fcμ–J interaction.

a Lack of Ca²⁺ results in no binding between CD5L and Fcμ–J in a pull-down assay. This experiment has been repeated at least three times. b Mutations in putative Ca²⁺-binding sites in SRCR1 (D50A/D51A and E118A) do not influence CD5L-Fcμ–J interaction. However, mutations in SRCR3’s cation-binding sites (D270A/D271A, E339A, and D270A/D271A/E339A) abolish interaction with Fcμ–J in the presence of Ca²⁺. This experiment has been repeated at least three times. c The R183A/V185N and F329N/G331S mutations disrupt the interaction with Fcμ–J, whereas C191S does not. This experiment has been repeated at least three times. d C191S (green) is capable of forming a complex with Fcμ–J similar to the wild-type (orange) in size-exclusion chromatography. SDS–PAGE analysis of the peak fractions from size-exclusion chromatography experiments is presented on the right. This experiment has been repeated at least three times. e SPR analyses of the interaction between human Fcμ–J and the C191S mutant in the presence of Ca²⁺.