An anti-antisigma factor in the response of the bacterium Myxococcus xanthus to blue light

Galbis-Martínez, Lilián; Galbis-Martínez, Marisa; Murillo, Francisco J.; Fontes, Marta

doi:10.1099/mic.0.2007/013359-0

Cited by 16 publications

(27 citation statements)

References 47 publications

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“…However, F and B are not ECF sigma factors. More recently, the response to blue light of the Myxococcus xanthus ECF sigma factor CarQ was proposed to be regulated by an anti-sigma (CarR) and an anti-anti-sigma (CarF) (12). However, CarF is not a two-component response regulator.…”

Section: Discussionmentioning

confidence: 99%

Dual Control of Sinorhizobium meliloti RpoE2 Sigma Factor Activity by Two PhyR-Type Two-Component Response Regulators

2010

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RpoE2 is an extracytoplasmic function (ECF) sigma factor involved in the general stress response of Sinorhizobium meliloti, the nitrogen-fixing symbiont of the legume plant alfalfa. RpoE2 orthologues are widely found among alphaproteobacteria, where they play various roles in stress resistance and/or host colonization. In this paper, we report a genetic and biochemical investigation of the mechanisms of signal transduction leading to S. meliloti RpoE2 activation in response to stress. We showed that RpoE2 activity is negatively controlled by two paralogous anti-sigma factors, RsiA1 (SMc01505) and RsiA2 (SMc04884), and that RpoE2 activation by stress requires two redundant paralogous PhyR-type response regulators, RsiB1 (SMc01504) and RsiB2 (SMc00794). RsiB1 and RsiB2 do not act at the level of rpoE2 transcription but instead interact with the anti-sigma factors, and we therefore propose that they act as anti-anti-sigma factors to relieve RpoE2 inhibition in response to stress. This model closely resembles a recently proposed model of activation of RpoE2-like sigma factors in Methylobacterium extorquens and Bradyrhizobium japonicum, but the existence of two pairs of anti-and anti-anti-sigma factors in S. meliloti adds an unexpected level of complexity, which may allow the regulatory system to integrate multiple stimuli.The capacity to sense and respond to environmental changes is essential for every living organism. In bacteria, a part of these responses occurs through modulation of initiation of gene transcription by changing the sigma factor associated with the core RNA polymerase. Sigma factors are dissociable subunits which provide the specificity of promoter recognition to RNA polymerase. Association of different sigma factors with the core enzyme makes it possible for the holoenzyme to recognize different promoters and express different sets of target genes. Sigma factors thus provide efficient mechanisms for simultaneous regulation of large numbers of genes (18). The so-called sigma 70 family of sigma factors includes primary sigma factors, which direct the transcription of housekeeping genes, as well as related alternative sigma factors which associate with the core RNA polymerase under various conditions, including stresses. The most abundant class of such alternative sigma factors is composed of structurally related proteins called extra-cytoplasmic function (ECF) sigma factors, as many of them control functions associated with various aspects of the cell surface or transport (20, 35).How stress stimuli are sensed and transduced to ECF sigma factors has been the subject of numerous studies. It appears that most ECF sigma factors share the important property of specifically interacting with a protein called anti-sigma factor, which plays a pivotal role in the control of sigma factor activity. In the absence of stimulus, the ECF sigma factor is kept inactive by interaction with its cognate anti-sigma factor. In the presence of stimulus, the anti-sigma factor gets inactivated, either via a mechanism involv...

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Section: Discussionmentioning

confidence: 99%

Dual Control of Sinorhizobium meliloti RpoE2 Sigma Factor Activity by Two PhyR-Type Two-Component Response Regulators

2010

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“…A characteristic feature of these proteins is the presence of several conserved histidine residues, which in CarF are predicted to localize in the cytoplasmic segments; several of these have been mutated and shown to be essential for function ( Fig. 1) (23,26). Some fatty acid hydroxylases and desaturases, with low or no overall sequence similarity to CarF, have a similar distribution of histidines that appear to be involved in a di-iron cluster and in enzyme activity (23,27,57).…”

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“…CarF participates, by an unknown mechanism, in the light inactivation of CarR, a membrane-associated anti-factor (10) with which CarF interacts physically (23,26). This liberates the CarRbound extracytoplasmic function (ECF) factor CarQ, which in association with core RNA polymerase (RNAP) activates transcription from P QRS , the promoter of the regulatory carQRS operon (10,30,38), and from P I , the promoter of the carotenogenic gene crtIb (24,41).…”

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confidence: 99%

“…Although the role of 1 O 2 in M. xanthus light-induced carotenogenesis has been hypothesized (18,32), it has not been directly demonstrated. Moreover, the chain of events linking blue light to CarF, the protein known to act earliest in the light-sensing pathway (23,26), remains to be established.…”

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confidence: 99%

“…It is a membrane-associated protein ( Fig. 1) with sequence similarity to eukaryotic proteins of unknown function called Kua, which constitute the protein superfamily PF10520 (Kua-UEV1_localn; http://pfam.sanger.ac.uk) (23,26,60). Although widely distributed in eukaryotes, bacterial members of this family have been identified only in M. xanthus (and the closely related species Stigmatella aurantiaca and Myxococcus fulvus), Bradyrhizobium japonicum, some Leptospira species, and a few other species (see Fig.…”

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CarF Mediates Signaling by Singlet Oxygen, Generated via Photoexcited Protoporphyrin IX, in Myxococcus xanthus Light-Induced Carotenogenesis

et al. 2012

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Conversion of the lycopene monocyclase of Myxococcus xanthus into a bicyclase

Iniesta

Cervantes

Murillo

2008

Appl Microbiol Biotechnol

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Depending on the cyclized hydrocarbon backbone ends, carotenoids can be acyclic, monocyclic, or bicyclic. Lycopene cyclases are the enzymes responsible for catalyzing the formation of cyclic carotenoids from acyclic lycopene. Myxococcus xanthus is a bacterium that accumulates monocyclic carotenoids such as a glycoside ester of myxobacton. We show here that this bacterium possesses a cyclase belonging to the group of the heterodimeric cyclases CrtYc and CrtYd. These two individual proteins are encoded by crtYc and crtYd, which are located in the carotenogenic carA operon of the carB-carA gene cluster, and the presence of both is essential for the cyclization of lycopene. CrtYc and CrtYd from M. xanthus form a heterodimeric cyclase with beta-monocyclic activity, which converts lycopene into monocyclic gamma-carotene, but not into bicyclic beta-carotene like most beta-cyclases. This is an unusual case where two different proteins constitute a lycopene cyclase enzyme with monocyclic activity. We were able to convert this lycopene monocyclase into a lycopene bicyclase enzyme producing beta-carotene, by fusing both proteins with an extra transmembrane domain. The chimeric protein appears to allow a proper membranal disposition of both CrtYc and CrtYd, to perform two cyclization reactions, while a hybrid without the extra transmembrane helix performs only one cyclization.

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An anti-antisigma factor in the response of the bacterium Myxococcus xanthus to blue light

Cited by 16 publications

References 47 publications

Dual Control of Sinorhizobium meliloti RpoE2 Sigma Factor Activity by Two PhyR-Type Two-Component Response Regulators

Dual Control of Sinorhizobium meliloti RpoE2 Sigma Factor Activity by Two PhyR-Type Two-Component Response Regulators

CarF Mediates Signaling by Singlet Oxygen, Generated via Photoexcited Protoporphyrin IX, in Myxococcus xanthus Light-Induced Carotenogenesis

Conversion of the lycopene monocyclase of Myxococcus xanthus into a bicyclase

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