Component of the ska-1 complex, a microtubule-binding subcomplex of the outer kinetochore that is essential for proper chromosome segregation. Required for timely anaphase onset during mitosis, when chromosomes undergo bipolar attachment on spindle microtubules leading to silencing of the spindle checkpoint. The ska-1 complex is a direct component of the kinetochore-microtubule interface and directly associates with microtubules as oligomeric assemblies. The complex facilitates the processive movement of microspheres along a microtubule in a depolymerization-coupled manner. Affinity for microtubules is synergistically enhanced in the presence of the ndc-80 complex and may allow the ndc-80 complex to track depolymerizing microtubules. In the complex, it mediates the interaction with microtubules. Component of the ska1 complex, composed of two copies of ska-1 and a single copy of ska-3. The core complex associates with microtubules and may form dimeric assemblies. Interacts with ska-3 and microtubules. Belongs to the SKA1 family.