Calcium tips the balance: a microtubule plus end to lattice binding switch operates in the carboxyl terminus of BPAG1n4.

Microtubules (MTs) are integral to numerous cellular functions, such as cell adhesion, differentiation and intracellular transport. Their dynamics are largely controlled by diverse MT-interacting proteins, but the signalling mechanisms that regulate these interactions remain elusive. In this report, we identify a rapid, calcium-regulated switch between MT plus end interaction and lattice binding within the carboxyl terminus of BPAG1n4. This switch is EF-hand dependent, and mutations of the EF-hands abolish this dynamic behaviour. Our study thus uncovers a new, calcium-dependent regulatory mechanism for a spectraplakin, BPAG1n4, at the MT plus end.