Solution structure of the kinase‐associated domain 1 of mouse microtubule‐associated protein/microtubule affinity‐regulating kinase 3

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Abstract
Microtubule‐associated protein/microtubule affinity‐regulating kinases (MARKs)/PAR‐1 are common regulators of cell polarity that are conserved from nematode to human. All of these kinases have a highly conserved C‐terminal domain, which is termed the kinase‐associated domain 1 (KA1), although its function is unknown. In this study, we determined the solution structure of the KA1 domain of mouse MARK3 by NMR spectroscopy. We found that ∼50 additional residues preceding the previously defined KA1 domain are required for its proper folding. The newly defined KA1 domain adopts a compact α+β structure with a βαββββα topology. We also found a characteristic hydrophobic, concave surface surrounded by positively charged residues. This concave surface includes the highly conserved Glu‐Leu‐Lys‐Leu motif at the C terminus, indicating that it is important for the function of the KA1 domain.