Microtubule inner protein (MIP) part of the dynein-decorated doublet microtubules (DMTs) in cilia axoneme, which is required for motile cilia beating (By similarity). May play a role in the beating of primary cilia and thereby be involved in the establishment of organ laterality during embryogenesis (By similarity). Interacts with PIERCE1 and PIERCE2; the interactions link outer dynein arms docking complex (ODA-DC) to the internal microtubule inner proteins (MIP) in cilium axoneme. Belongs to the CFAP53 family. Truncated N-terminus.