Fig. 4.
Population of oligomers during the formation of HSP18.1:Luc complexes. A Analogous tandem-MS experiments to that in Fig. 3B performed for different isolations (c.f. Fig. 2B) of a 30 s incubation of HSP18.1 and Luc, at a 1∶1 ratio. An expansion of the [HSP18.1](X-1)[Luc]Y region is shown. A range of complexes and higher-order oligomers are identified, with the labelling referring to the parent oligomer. Theoretical peak positions arising from dissociation of [HSP18.1]12[Luc]1 are indicated by dashed white lines, and do not correspond to the charge state series observed. This suggests this species is not formed during protection of Luc. B Quantifying the stripped oligomers shows that the abundance of complexes with an even number of subunits is higher than those with an odd number at all timepoints. However this difference is greatest at earlier time points. Overlaying the parameters determined in Fig. 2B for the binding and augmentation steps in complex formation gives an excellent fit, suggesting that dimers are involved in the client binding process.