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J Biol Chem. 2018 Nov 23;293(47):18353-18364. doi: 10.1074/jbc.RA118.005651. Epub 2018 Oct 10.

Substrate priming enhances phosphorylation by the budding yeast kinases Kin1 and Kin2.

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From the Department of Pharmacology, Yale School of Medicine, New Haven, Connecticut 06520.
the Department of Biology, Quinnipiac University, Hamden, Connecticut 06518, and.
the Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill, North Carolina 27599.
From the Department of Pharmacology, Yale School of Medicine, New Haven, Connecticut 06520,


Multisite phosphorylation of proteins is a common mechanism for signal integration and amplification in eukaryotic signaling networks. Proteins are commonly phosphorylated at multiple sites in an ordered manner, whereby phosphorylation by one kinase primes the substrate by generating a recognition motif for a second kinase. Here we show that substrate priming promotes phosphorylation by Saccharomyces cerevisiae Kin1 and Kin2, kinases that regulate cell polarity, exocytosis, and the endoplasmic reticulum (ER) stress response. Kin1/Kin2 phosphorylated substrates within the context of a sequence motif distinct from those of their most closely related kinases. In particular, the rate of phosphorylation of a peptide substrate by Kin1/Kin2 increased >30-fold with incorporation of a phosphoserine residue two residues downstream of the phosphorylation site. Recognition of phosphorylated substrates by Kin1/Kin2 was mediated by a patch of basic residues located in the region of the kinase αC helix. We identified a set of candidate Kin1/Kin2 substrates reported to be dually phosphorylated at sites conforming to the Kin1/Kin2 consensus sequence. One of these proteins, the t-SNARE protein Sec9, was confirmed to be a Kin1/Kin2 substrate both in vitro and in vivo Sec9 phosphorylation by Kin1 in vitro was enhanced by prior phosphorylation at the +2 position. Recognition of primed substrates was not required for the ability of Kin2 to suppress the growth defect of secretory pathway mutants but was necessary for optimal growth under conditions of ER stress. These results suggest that at least some endogenous protein substrates of Kin1/Kin2 are phosphorylated in a priming-dependent manner.


SNARE proteins; Sec9; endoplasmic reticulum stress (ER stress); exocytosis; kinase priming; phosphorecognition; protein kinase; protein phosphorylation; signal transduction; yeast

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