Serine-Threonine Kinase Encoded by a Split hipA Homologous Gene of Escherichia coli Inhibits Tryptophanyl-tRNA Synthetase

ABSTRACT: Type II toxin – antitoxin modules encode a stable toxin that inhibits translation, replication or cell wall synthesis and an unstable protein antitoxin that neutralizes the toxin by direct protein – protein contact. The hipBA module of Escherichia coli K-12 codes for HipA, a eukaryote-like serine/threonine protein kinase that phosphorylates and inhibits glutamyl-tRNA synthetase. Induction of hipA leads to a reduced level of charged glutamyl tRNA that, in turn, inhibits translation, induces RelA-dependent (p)ppGpp synthesis and multidrug tolerance (persistence). Here, we describe the discovery of a three-component TA module hipBST of E. coli O127:H6 strain E2348/69 that encodes HipT, which exhibits sequence similarity with the C-terminal part of HipA. We show that HipT is a kinase that phosphorylates tryptophanyl-tRNA synthetase in vitro at conserved serine residue. Consistently, induction of hipT inhibits cell growth, stimulates production of stringent factor (p)ppGpp and induces persistence. Remarkably, the gene immediately upstream of hipT, called hipS, encodes a small protein that exhibits sequence similarity with the C-terminal part of HipA. Unexpectedly, HipT kinase is neutralized by HipS in vivo whereas the third component, HipB0127, encoded by the first gene of the operon, does not counteract HipT kinase. However, HipB contains a HTH DNA-binding domain and may function to autoregulate the hipBST operon. Thus, hipA has been split into two genes, hipS and hipT that function as a toxin – antitoxin pair.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Escherichia Coli

SUBMITTER: Nicolas Nalpas  

LAB HEAD: Boris Macek

PROVIDER: PXD012023 | Pride | 2019-06-24

REPOSITORIES: Pride