Cyclic-di-GMP binding induces structural rearrangements in the PlzA and PlzC proteins of the Lyme disease and relapsing fever spirochetes: a possible switch mechanism for c-di-GMP-mediated effector functions

Abstract

The c-di-GMP network of Borrelia burgdorferi, a causative agent of Lyme disease, consists of Rrp1, a diguanylate cyclase/response regulator; Hpk1, a histidine kinase; PdeA and PdeB, c-di-GMP phosphodiesterases; and PlzA, a PilZ domain c-di-GMP receptor. Borrelia hermsii, a causative agent of tick-borne relapsing fever, possesses a putative c-di-GMP regulatory network that is uncharacterized. While B. burgdorferi requires c-di-GMP to survive within ticks, the associated effector mechanisms are poorly defined. Using site-directed mutagenesis, size exclusion chromatography, isothermal titration calorimetry and fluorescence resonance energy transfer, we investigate the interaction of c-di-GMP with the Borrelia PilZ domain-containing Plz proteins: B. burgdorferi PlzA and B. hermsii PlzC. The Plz proteins were determined to be monomeric in their apo and holo forms and to bind c-di-GMP with high affinity with a 1:1 stoichiometry. C-di-GMP binding induced structural rearrangements in PlzA and PlzC. C-di-GMP binding proved to be dependent on positive charge at R of the PilZ domain motif, RxxxR. Comparative sequence analyses led to the identification of Borrelia consensus sequences for the PilZ domain signature motifs. This study provides insight into c-di-GMP:Plz receptor interaction and identifies a possible switch mechanism that may regulate Plz protein effector functions.

Positive and Negative Regulation of Glycerol Utilization by the c-di-GMP Binding Protein PlzA in Borrelia burgdorferi

“…We postulate that PlzA indirectly regulates glp and bosR expression by interacting with an as-yet-unidentified partner(s) and that conformational changes in response to the presence or absence of c-di-GMP switches between the positive and negative roles of PlzA. In this regard, conformational change of PlzA of B. burgdorferi and PlzC of Borrelia hermsii upon binding to c-di-GMP has been demonstrated recently by Mallory et al (33). It is likely that PlzA interacts with more than a single partner, because it exerts its effect on a diverse range of downstream processes, such as glp and bosR expression, N-acetylglucosamine utilization, cell envelope synthesis, motility, and osmolarity (11,13,14,19,21,28).…”

“…Thus, c-di-GMP appears to play a role in the catabolic switch of B. burgdorferi where a classical catabolic repression system is lacking. Of note, different functions in bound and unbound forms of PlzA in ticks and mammals have been proposed by Mallory et al (33), based on the fact that the rrp1 mutant and the plzA mutant have different phenotypes in the enzootic cycle of B. burgdorferi (5,6,19). In some isolates of B. burgdorferi, there is an additional copy of PilZ-containing c-di-GMP receptor, PlzB, and a recent report suggests that it could not complement the function of PlzA (34).…”

The Borrelia burgdorferi c-di-GMP Binding Receptors, PlzA and PlzB, Are Functionally Distinct

“…PlzA is a 29.6 kDa (261 aa) stand-alone PilZ domain protein (i.e., lacks other identifiable conserved functional domains) that is chromosomally encoded ( B. burgdorferi B31 ORF designation, BB0733). The tick-borne relapsing fever spirochetes encode a related c-di-GMP receptor designated as PlzC that is also encoded by a linear chromosome carried gene (Freedman et al, 2009 ; Mallory et al, 2016 ). PlzA has 69% amino acid identity to PlzC.…”

Gene Regulation, Two Component Regulatory Systems, and Adaptive Responses in Treponema Denticola

“…Perhaps most notable is the potential global regulatory role of the secondary messenger, c-di-GMP, which most certainly plays an important role in the biology and pathogenesis of T. denticola (Bian et al 2013). C-di-GMP mediated regulation has been studied in depth in a long and diverse list of bacteria, including spirochete species associated with Lyme disease and relapsing fever (Caimano et al 2015;Kostick et al 2011;Mallory et al 2016;Pitzer et al 2011;Rogers et al 2009;Ryjenkov et al 2005;Sultan et al 2010). C-di-GMP is produced by diguanylate cyclases (DGC) which can be identified by the presence of the signature GGDEF domain (Hengge 2009).…”