Dataset Information

Decoding Biomass-Sensing Regulons of Clostridium thermocellum Alternative Sigma-I Factors in a Heterologous Bacillus subtilis Host System.

ABSTRACT: The Gram-positive, anaerobic, cellulolytic, thermophile Clostridium (Ruminiclostridium) thermocellum secretes a multi-enzyme system called the cellulosome to solubilize plant cell wall polysaccharides. During the saccharolytic process, the enzymatic composition of the cellulosome is modulated according to the type of polysaccharide(s) present in the environment. C. thermocellum has a set of eight alternative RNA polymerase sigma (?) factors that are activated in response to extracellular polysaccharides and share sequence similarity to the Bacillus subtilis ?I factor. The aim of the present work was to demonstrate whether individual C. thermocellum ?I-like factors regulate specific cellulosomal genes, focusing on C. thermocellum ?I6 and ?I3 factors. To search for putative ?I6- and ?I3-dependent promoters, bioinformatic analysis of the upstream regions of the cellulosomal genes was performed. Because of the limited genetic tools available for C. thermocellum, the functionality of the predicted ?I6- and ?I3-dependent promoters was studied in B. subtilis as a heterologous host. This system enabled observation of the activation of 10 predicted ?I6-dependent promoters associated with the C. thermocellum genes: sigI6 (itself, Clo1313_2778), xyn11B (Clo1313_0522), xyn10D (Clo1313_0177), xyn10Z (Clo1313_2635), xyn10Y (Clo1313_1305), cel9V (Clo1313_0349), cseP (Clo1313_2188), sigI1 (Clo1313_2174), cipA (Clo1313_0627), and rsgI5 (Clo1313_0985). Additionally, we observed the activation of 4 predicted ?I3-dependent promoters associated with the C. thermocellum genes: sigI3 (itself, Clo1313_1911), pl11 (Clo1313_1983), ce12 (Clo1313_0693) and cipA. Our results suggest possible regulons of ?I6 and ?I3 in C. thermocellum, as well as the ?I6 and ?I3 promoter consensus sequences. The proposed -35 and -10 promoter consensus elements of ?I6 are CNNAAA and CGAA, respectively. Additionally, a less conserved CGA sequence next to the C in the -35 element and a highly conserved AT sequence three bases downstream of the -10 element were also identified as important nucleotides for promoter recognition. Regarding ?I3, the proposed -35 and -10 promoter consensus elements are CCCYYAAA and CGWA, respectively. The present study provides new clues for understanding these recently discovered alternative ?I factors.

SUBMITTER: Munoz-Gutierrez I

PROVIDER: S-EPMC4711584 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Decoding Biomass-Sensing Regulons of Clostridium thermocellum Alternative Sigma-I Factors in a Heterologous Bacillus subtilis Host System.

Muñoz-Gutiérrez Iván I Ortiz de Ora Lizett L Rozman Grinberg Inna I Garty Yuval Y Bayer Edward A EA Shoham Yuval Y Lamed Raphael R Borovok Ilya I

PloS one 20160105 1

The Gram-positive, anaerobic, cellulolytic, thermophile Clostridium (Ruminiclostridium) thermocellum secretes a multi-enzyme system called the cellulosome to solubilize plant cell wall polysaccharides. During the saccharolytic process, the enzymatic composition of the cellulosome is modulated according to the type of polysaccharide(s) present in the environment. C. thermocellum has a set of eight alternative RNA polymerase sigma (σ) factors that are activated in response to extracellular polysac ...[more]

PMID: 26731480

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Project description:Environmental awareness is an essential attribute of all organisms. The homeoviscous adaptation system of Bacillus subtilis provides a powerful experimental model for the investigation of stimulus detection and signaling mechanisms at the molecular level. These bacteria sense the order of membrane lipids with the transmembrane (TM) protein DesK, which has an N-terminal sensor domain and an intracellular catalytic effector domain. DesK exhibits autokinase activity as well as phosphotransferase and phosphatase activities toward a cognate response regulator, DesR, that controls the expression of an enzyme that remodels membrane fluidity when the temperature drops below ∼30°C. Membrane fluidity signals are transmitted from the DesK sensor domain to the effector domain via rotational movements of a connecting 2-helix coiled coil (2-HCC). Previous molecular dynamic simulations suggested important roles for TM prolines in transducing the initial signals of membrane fluidity status to the 2-HCC. Here, we report that individual replacement of prolines in DesKs TM1 and TM5 helices by alanine (DesKPA) locked DesK in a phosphatase-ON state, abrogating membrane fluidity responses. An unbiased mutagenic screen identified the L174P replacement in the internal side of the repeated heptad of the 2-HCC structure that alleviated the signaling defects of every transmembrane DesKPA substitution. Moreover, substitutions by proline in other internal positions of the 2-HCC reestablished the kinase-ON state of the DesKPA mutants. These results imply that TM prolines are essential for finely tuned signal generation by the N-terminal sensor helices, facilitating a conformational control by the metastable 2-HCC domain of the DesK signaling state.IMPORTANCE Signal sensing and transduction is an essential biological process for cell adaptation and survival. Histidine kinases (HK) are the sensory proteins of two-component systems that control many bacterial responses to different stimuli, like environmental changes. Here, we focused on the HK DesK from Bacillus subtilis, a paradigmatic example of a transmembrane thermosensor suited to remodel membrane fluidity when the temperature drops below 30°C. DesK provides a tractable system for investigating the mechanism of transmembrane signaling, one of the majors interrogates in biology to date. Our studies demonstrate that transmembrane proline residues modulate the conformational switch of a 2-helix coiled-coil (2-HCC) structural motif that controls input-output in a variety of HK. Our results highlight the relevance of proline residues within sensor domains and could inspire investigations of their role in different signaling proteins.

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Dataset Information

Decoding Biomass-Sensing Regulons of Clostridium thermocellum Alternative Sigma-I Factors in a Heterologous Bacillus subtilis Host System.

Publications

Decoding Biomass-Sensing Regulons of Clostridium thermocellum Alternative Sigma-I Factors in a Heterologous Bacillus subtilis Host System.

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