A Crosslinking Mass Spectrometry Protocol for the Structural Analysis of Microtubule-Associated Proteins.

Microtubule-associated proteins (MAPs) engage microtubules (MTs) to regulate both the MT state and wide variety of cytoskeletal functions. A comprehensive understanding of MAPs function requires the structural characterization of physical contacts MAPs make with other proteins, particularly when engaged with the microtubule (MT) lattice. Most of the interaction between MAPs and MTs evade classical structural determination techniques, as the interactions can be both heterogenous and sub-stoichiometric. Crosslinking mass spectrometry (XL-MS) can aid in MAP-MT structure analysis by providing a wealth of residue-based distance restraints. This protocol provides an XL-MS workflow for accurate and unbiased sampling of an equilibrated MAP-MT interaction, involving modifications to the preparation and validation of a MAP-MT construct suitable for crosslinking with fast-sampling heterobifunctional crosslinkers. The distance restrains obtained by this protocol can be used to generate accurate models assembled with an integrative structural modeling approach.