No Conventional Function for the Conventional Kinesin?

A paper by DeGiorgis et al. (DeGiorgis JA, Petukhova TA, Evans TA, Reese TS. Kinesin‐3 is an organelle motor in the squid giant axon. Traffic 2008; DOI: 10.1111/j.1600‐0854.2008.00809.x) in this issue of Traffic reports on the identification and function of a second squid kinesin, a kinesin‐3 motor. As expected, the newly discovered motor associates with axoplasmic organelles in situ and powers motility along microtubules of vesicles isolated from squid axoplasm. Less expected was the finding that kinesin‐3 may be the predominant motor for anterograde organelle movement in the squid axon, which challenges the so far undisputed view that this function is fulfilled by the conventional kinesin, kinesin‐1. These novel findings let us wonder what the real function of kinesin‐1 – the most abundant motor in squid axons – actually is.