The Legionella pneumophila kai operon is implicated in stress response and confers fitness in competitive environments

By Maria Loza-Correa, T. Sahr, Monica Rolando, C. Daniels, P. Petit, T. Skarina, L. Valero, Delphine Dervins-Ravault, N. Honoré, A. Savchenko and 1 more. 2013

38 citations recorded by the source corpus.

Summary Legionella pneumophila uses aquatic protozoa as replication niche and protection from harsh environments. Although L. pneumophila is not known to have a circadian clock, it encodes homologues of the KaiBC proteins of Cyanobacteria that regulate circadian gene expression. We show that L. pneumophila kaiB, kaiC and the downstream gene lpp1114, are transcribed as a unit under the control of the stress sigma factor RpoS. KaiC and KaiB of L. pneumophila do not interact as evidenced by yeast and bacterial two-hybrid analyses. Fusion of the C-terminal residues of cyanobacterial KaiB to Legionella KaiB restores their interaction. In contrast, KaiC of L. pneumophila conserved autophosphorylation activity, but KaiB does not trigger the dephosphorylation of KaiC like in Cyanobacteria. The crystal structure of L. pneumophila KaiB suggests that it is an oxidoreductase-like protein with a typical thioredoxin fold. Indeed, mutant analyses revealed that the kai operon-encoded proteins increase fitness of L. pneumophila in competitive environments, and confer higher resistance to oxidative and sodium stress. The phylogenetic analysis indicates that L. pneumophila KaiBC resemble Synechosystis KaiC2B2 and not circadian KaiB1C1. Thus, the L. pneumophila Kai proteins do not encode a circadian clock, but enhance stress resistance and adaption to changes in the environments.

Subfields: Endocrinology, Molecular Biology

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Citations in the corpus

• Predicting multiple conformations via sequence clustering and AlphaFold2 (2023, neutral): “By contrast, a KaiB variant from Legionella pneumophila that has previously been crystallized in the FS state 37 was predicted with high confidence for the FS state.”
• Minimal tool set for a prokaryotic circadian clock (2016, background): “Free KaiB1 crystallizes in a unique fold, but can adopt a fold switched state, which is a prerequisite for KaiC binding and is similar to the thioredoxin like fold observed in KaiB2 crystals [138, 139].”