Protein–protein interactions between intermediate chains and the docking complex of Chlamydomonas flagellar outer arm dynein

• The IC1/IC2 complex is bound to the outer-dynein-arm docking complex.
• IC1 binds a specific site on the doublet microtubules.
• Specific OAD-microtubule binding is achieved by multiple weak interactions.

Outer arm dynein (OAD) is bound to specific loci on outer-doublet-microtubules by interactions at two sites: via intermediate chain 1 (IC1) and the outer dynein arm docking complex (ODA-DC). Studies using Chlamydomonas mutants have suggested that the individual sites have rather weak affinities for microtubules, and therefore strong OAD attachment to microtubules is achieved by their cooperation. To test this idea, we examined interactions between IC1, IC2 (another intermediate chain) and ODA-DC using recombinant proteins. Recombinant IC1 and IC2 were found to form a 1:1 complex, and this complex associated with ODA-DC in vitro. Binding of IC1 to mutant axonemes revealed that there are specific binding sites for IC1. From these data, we propose a novel model of OAD-outer doublet association.

Structured summary of protein interactions:IC2 physically interacts with DC2 and DC1 by anti bait coimmunoprecipitation (View interaction)DC2 physically interacts with IC2 and IC1 by anti bait coimmunoprecipitation (View interaction)IC2 and IC1 physically interact by cross-linking study (View interaction)IC2 and DC1 physically interact by cross-linking study (View interaction)DC2 and DC1 physically interact by cross-linking study (View Interaction: 1, 2)DC1 and IC1 physically interact by cross-linking study (View interaction)IC2 binds to IC1 by anti bait coimmunoprecipitation (View interaction)IC2, DC1 and DC2 physically interact by cross-linking study (View interaction)DC2, IC1 and DC1 physically interact by cross-linking study (View interaction)