The MIA complex functions in the I1 dynein phosphoregulatory pathway and interacts with multiple axonemal proteins. (A) Untreated flagella (fla), untreated axonemes (axo), and axonemes treated with the kinase inhibitor DRB were probed with the anti-IC138 antibody. In the mia untreated axonemes, IC138 migrates in multiple forms in a manner similar to pf17. In contrast, wild-type axonemes show a compact IC138 profile. DRB treatment results in a shift in migration of IC138, indicating that these multiple forms of IC138 are caused by phosphorylation. (B) Immunoblot analyses indicate that CK1, PP2A (B and C subunits [sub]), and PP1 are assembled normally in the mia mutants. (C) Isolated wild-type axonemes treated with or without 5 mM EDC were probed with the FAP100 and FAP73 antibodies. Upon EDC exposure, both Mia proteins form some cross-linked products (red arrowheads), indicating that the MIA complex is in direct contact with multiple axonemal proteins. We could not detect the cross-linked products between I1 dynein subunits and the Mia proteins as solid bands on these blots. Black arrows indicate the un–cross-linked FAP100 and FAP73. Ab, antibody; wt, wild type.