AUTHOR=Zheng Weihao , Cai Xiaodan , Li Shuiming , Li Zigang 

TITLE=Autophosphorylation Mechanism of the Ser/Thr Kinase Stk1 From Staphylococcus aureus

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.00758

DOI=10.3389/fmicb.2018.00758

ISSN=1664-302X

ABSTRACT=<p>The eukaryotic-like Ser/Thr kinase Stk1 is crucial for virulence, cell wall biosynthesis, and drug susceptibility in methicillin-resistant <italic>Staphylococcus aureus</italic> (<italic>S. aureus</italic>) (MRSA). Importantly, MRSA lacking Stk1 become sensitive to β-lactam antibiotics, implying that Stk1 could be an alternative target for combination therapy. However, the autophosphorylation mechanism of Stk1 remains elusive. Using a phosphoproteomic study, we identified six <italic>in vivo</italic> phosphorylated activation loop residues (Ser159, Thr161, Ser162, Thr164, Thr166, and Thr172) of Stk1, which are also phosphorylated <italic>in vitro</italic>. We further showed that <italic>cis</italic> autophosphorylation of Thr172 in the GT/S motif is essential for self-activation and kinase activity of Stk1 kinase domain (Stk1-KD), whereas the <italic>trans</italic> autophosphorylation of other activation loop serines/threonines are required for the optimal kinase activity of Stk1-KD. Moreover, substitution of the activation loop serines/threonines impaired <italic>in vivo</italic> autophosphorylation activity of kinase variants, while T172A and T172D variants were unable to autophosphorylate in the cellular content, underlining the essential role of Thr172 for Stk1 activity <italic>in vivo</italic>. This study provides insights into molecular basis for regulation of Stk1 activity from <italic>S. aureus</italic>.</p>