An amino‐terminal threonine/serine motif is necessary for activity of the Crp/Fnr homolog, MrpC and forMyxococcus xanthusdevelopmental robustness

Abstract

The Crp/Fnr family of transcriptional regulators play central roles in transcriptional control of diverse physiological responses, and are activated by a surprising diversity of mechanisms. MrpC is a Crp/ Fnr homolog that controls the Myxococcus xanthus developmental program. A long-standing model proposed that MrpC activity is controlled by the Pkn8/ Pkn14 serine/threonine kinase cascade, which phosphorylates MrpC on threonine residue(s) located in its extreme amino-terminus. In this study, we demonstrate that a stretch of consecutive threonine and serine residues, T 21 T 22 S 23 S 24, is necessary for MrpC activity by promoting efficient DNA binding. Mass spectrometry analysis indicated the TTSS motif is not directly phosphorylated by Pkn14 in vitro but is necessary for efficient Pkn14-dependent phosphorylation on several residues in the remainder of the protein. In an important correction to a long-standing model, we show Pkn8 and Pkn14 kinase activities do not play obvious roles in controlling MrpC activity in wild-type M. xanthus under laboratory conditions. Instead, we propose Pkn14 modulates MrpC DNA binding in response to unknown environmental conditions. Interestingly, substitutions in the TTSS motif caused developmental defects that varied between biological replicates, revealing that MrpC plays a role in promoting a robust developmental phenotype.

An ambruticin-sensing complex modulates Myxococcus xanthus development and mediates myxobacterial interspecies communication

“…It has been shown that MrpC is phosphorylated at its N-terminus by the serine/threonine protein kinase (STPK) Pkn14 in a STPK cascade which consists of kinases Pkn8/Pkn14 33 – 35 . Recently, a cluster of threonines and serines (TTSS motif) in the amino‐terminal region was identified to be essential for MrpC activity in vivo 36 . The motif was not phosphorylated by Pkn14, but was necessary for Pkn14-mediated phosphorylation of other sites in MrpC.…”

Regulation of late‐acting operons by three transcription factors and a CRISPR‐Cas component during Myxococcus xanthus development

“…The in vivo interactions of MrpC and Nla6‐P with FruA are difficult to predict. MrpC is phosphorylated on several residues and may bind a small molecule (Feeley et al., 2019). Nla6 has an N‐terminal response regulator receiver domain and a central AAA + ATPase domain preceding its C‐terminal DBD (Caberoy et al., 2003), but neither a histidine kinase nor a small‐molecule capable of phosphorylating the receiver domain has been found (Sarwar & Garza, 2012).…”

An Intracellular Sensing and Signal Transduction System That Regulates the Metabolism of Polycyclic Aromatic Hydrocarbons in Bacteria

“…The regulators DPR-1 and DPR-2 belong to the CRP/FNR family of proteins. CRP/FNR proteins are extraordinary in that they respond to a broad spectrum of intracellular and exogenous signals, such as cAMP, anoxia, redox state, oxidative and nitrosative stress, nitric oxide (NO), carbon monoxide (CO), 2-oxoglutarate, and temperature ( 49 – 56 ). Previously, regulators in this family have been associated with several processes, including the regulation of the anaerobic degradation of benzoate and cyclohexanecarboxylate in Rhodopseudomonas palustri ( 57 ) as well as the dehalorespiration of halogenated aromatic compounds in Desulfitobacterium ( 58 ).…”