Molecular Biophysics
Functionally specific binding regions of microtubule-associated protein 2c exhibit distinct conformations and dynamics

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Microtubule-associated protein 2c (MAP2c) is a 49-kDa intrinsically disordered protein regulating the dynamics of microtubules in developing neurons. MAP2c differs from its sequence homologue Tau in the pattern and kinetics of phosphorylation by cAMP-dependent protein kinase (PKA). Moreover, the mechanisms through which MAP2c interacts with its binding partners and the conformational changes and dynamics associated with these interactions remain unclear. Here, we used NMR relaxation and paramagnetic relaxation enhancement techniques to determine the dynamics and long-range interactions within MAP2c. The relaxation rates revealed large differences in flexibility of individual regions of MAP2c, with the lowest flexibility observed in the known and proposed binding sites. Quantitative conformational analyses of chemical shifts, small-angle X-ray scattering (SAXS), and paramagnetic relaxation enhancement measurements disclosed that MAP2c regions interacting with important protein partners, including Fyn tyrosine kinase, plectin, and PKA, adopt specific conformations. High populations of polyproline II and α-helices were found in Fyn- and plectin-binding sites of MAP2c, respectively. The region binding the regulatory subunit of PKA consists of two helical motifs bridged by a more extended conformation. Of note, although MAP2c and Tau did not differ substantially in their conformations in regions of high sequence identity, we found that they differ significantly in long-range interactions, dynamics, and local conformation motifs in their N-terminal domains. These results highlight that the N-terminal regions of MAP2c provide important specificity to its regulatory roles and indicate a close relationship between MAP2c's biological functions and conformational behavior.

microtubule-associated protein (MAP)
nuclear magnetic resonance (NMR)
small-angle X-ray scattering (SAXS)
Tau protein (Tau)
protein conformation
NMR relaxation
paramagnetic relaxation enhancement (PRE)

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This work was supported in part by Czech Science Foundation Grant GA15-14974S. The authors declare that they have no conflicts of interest with the contents of this article.

The small angle scattering data and models reported in this paper have been submitted to the Small Angle Scattering Biological Data Bank under SASBD accession numbers SASDD62, SASDD72, SASDD82, SASDD92, SASDDA2, SASDDB2, and SASDDC2.

The data reported in this paper have been submitted to the Biological Magnetic Resonance Bank under BMRB accession number 27350.

1

These authors contributed equally to this work.

2

The stay of this author at the University Grenoble Alps was supported by the European Union's Horizon 2020 Research and Innovation Programme under Grant Agreement 692068.

3

Present address: École Normale Supérieure, Dépt. de chimie, 24 rue Lhomond, 75005 Paris, France.

4

Supported by European Regional Development Fund-Project “CIISB4HEALTH” Grant CZ.02.1.01/0.0/0.0/16_013/0001776.