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LicT, a Bacillus subtilis transcriptional antiterminator protein of the BglG family.

ABSTRACT: Gene licS of Bacillus subtilis encodes an excreted Beta-1,3-1,4-endoglucanase necessary for lichenan utilization. Upstream of licS we found a gene (termed licT) together with its promoter which encodes a transcriptional antiterminator of the BglG family. Genes licT and licS are separated by a palindromic sequence (lic-t) reminiscent of transcriptional terminators recognized by the antiterminator proteins of the BglG family. The LicT protein can prevent termination at terminator lic-t and also at terminator t2 of the Escherichia coli bgl operon and BglG prevents termination at lic-t. The role of LicT in licS regulation by preventing termination at its terminator lic-t appears to be limited since expression of licS is inducible only two- to threefold. This limited regulation is mainly due to a high basal level of licS expression which can in part be attributed to the presence of a second promoter preceding licS and located downstream of lic-t. However, disruption of gene licT leads not only to loss of inducibility of licS but also to loss of growth on lichenan or on its degradation products, indicating its stringent role in beta-glucan utilization.

SUBMITTER: Schnetz K

PROVIDER: S-EPMC177893 | biostudies-other | 1996 Apr

REPOSITORIES: biostudies-other

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LicT, a Bacillus subtilis transcriptional antiterminator protein of the BglG family.

Schnetz K K Stülke J J Gertz S S Krüger S S Krieg M M Hecker M M Rak B B

Journal of bacteriology 19960401 7

Gene licS of Bacillus subtilis encodes an excreted Beta-1,3-1,4-endoglucanase necessary for lichenan utilization. Upstream of licS we found a gene (termed licT) together with its promoter which encodes a transcriptional antiterminator of the BglG family. Genes licT and licS are separated by a palindromic sequence (lic-t) reminiscent of transcriptional terminators recognized by the antiterminator proteins of the BglG family. The LicT protein can prevent termination at terminator lic-t and also at ...[more]

PMID: 8606172

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Project description:Previous characterization of Bacillus subtilis hemN, encoding a protein involved in oxygen-independent coproporphyrinogen III decarboxylation, indicated the presence of a second hemN-like gene (B. Hippler, G. Homuth, T. Hoffmann, C. Hungerer, W. Schumann, and D. Jahn, J. Bacteriol. 179:7181-7185, 1997). The corresponding hemZ gene was found to be split into the two potential open reading frames yhaV and yhaW by a sequencing error of the genome sequencing project. The hemZ gene, encoding a 501-amino-acid protein with a calculated molecular mass of 57,533 Da, complemented a Salmonella typhimurium hemF hemN double mutant under aerobic and anaerobic growth conditions. A B. subtilis hemZ mutant accumulated coproporphyrinogen III under anaerobic growth conditions. A hemN hemZ double mutant exhibited normal aerobic and anaerobic growth, indicating the presence of a third alternative oxygen-independent enzymatic system for coproporphyrinogen III oxidation. The hemY gene, encoding oxygen-dependent protoporphyrinogen IX oxidase with coproporphyrinogen III oxidase side activity, did not significantly contribute to this newly identified system. Growth behavior of hemY mutants revealed the presence of an oxygen-independent protoporphyrinogen IX oxidase in B. subtilis. A monocistronic hemZ mRNA, starting 31 bp upstream of the translational start codon, was detected. Reporter gene fusions of hemZ and hemN demonstrated a fivefold anaerobic induction of both genes under nitrate ammonifying growth conditions. No anaerobic induction was observed for fermentatively growing B. subtilis. The B. subtilis redox regulatory systems encoded by resDE, fnr, and ywiD were indispensable for the observed transcriptional induction. A redox regulation cascade proceeding from an unknown sensor via resDE, through fnr and ywiD to hemN/hemZ, is suggested for the observed coregulation of heme biosynthesis and the anaerobic respiratory energy metabolism. Finally, only hemZ was found to be fivefold induced by the presence of H(2)O(2), indicating further coregulation of heme biosynthesis with the formation of the tetrapyrrole enzyme catalase.

Project description:Manganese (Mn) is an essential element and is required for the virulence of many pathogens. In Bacillus subtilis, Mn(II) homeostasis is regulated by MntR, a Mn(II)-responsive, DNA-binding protein. MntR serves as both a repressor of Mn(II) uptake transporters and as a transcriptional activator for expression of two cation diffusion facilitator Mn(II) efflux pumps, MneP and MneS. Mutants lacking either mntR or both mneP and mneS are extremely sensitive to Mn(II) intoxication. Using transposon mutagenesis to select suppressors of Mn(II) sensitivity, we identified YceF, a TerC family membrane protein, as capable of providing Mn(II) resistance. Another TerC paralog, YkoY, is regulated by a Mn(II)-sensing riboswitch and is partially redundant in function with YceF. YkoY is regulated in parallel with an unknown function protein YybP, also controlled by a Mn(II)-sensing riboswitch. Strains lacking between one and five of these known or putative Mn(II) tolerance proteins (MneP, MneS, YceF, YkoY, and YybP) were tested for sensitivity to Mn(II) in growth assays and for accumulation of Mn(II) using inductively coupled plasma mass spectrometry. Loss of YceF and, to a lesser extent, YkoY, sensitizes cells lacking the MneP and MneS efflux transporters to Mn(II) intoxication. This sensitivity correlates with elevated intracellular Mn(II), consistent with the suggestion that TerC proteins function in Mn(II) efflux.IMPORTANCE Manganese homeostasis is primarily regulated at the level of transport. Bacillus subtilis MntR serves as a Mn(II)-activated repressor of importer genes (mntH and mntABC) and an activator of efflux genes (mneP and mneS). Elevated intracellular Mn(II) also binds to Mn-sensing riboswitches to activate transcription of yybP and ykoY, which encodes a TerC family member. Here, we demonstrate that two TerC family proteins, YceF and YkoY, help prevent Mn(II) intoxication. TerC family proteins are widespread in bacteria and may influence host-pathogen interactions, but their effects on Mn(II) homeostasis are unclear. Our results suggest that TerC proteins work by Mn(II) export under Mn(II) overload conditions to help alleviate toxicity.

Dataset Information

LicT, a Bacillus subtilis transcriptional antiterminator protein of the BglG family.

Publications

LicT, a Bacillus subtilis transcriptional antiterminator protein of the BglG family.

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