Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.13.3 (histidine kinase)
2,405 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Anabaena sp. PCC 7120 was mutagenized by transposon Tn5-1087b, generating a mutant whose heterocysts lack the envelope polysaccharide layer. The transposon was located between nucleotides 342 and 343 of alr0117, a 918 bp gene encoding a histidine kinase for a two-component regulatory system. Complementation of the mutant with a DNA fragment containing alr0117 and targeted inactivation of the gene confirmed that alr0117 is involved in heterocyst development. RT-PCR showed that alr0117 was constitutively expressed in the presence or absence of a combined-nitrogen source. hepA and patB, the two genes turned on during wild-type heterocyst development, were no longer activated in an alr0117-null mutant. The two-component signal transduction system involving alr0117 may control the formation of the envelope polysaccharide layer and certain late events essential to the function of heterocysts.
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PMID:alr0117, a two-component histidine kinase gene, is involved in heterocyst development in Anabaena sp. PCC 7120. 1476 23

Photoreceptor chromoproteins undergo light-induced conformational changes that result in a modulation of protein interaction and enzymatic activity. Bacterial phytochromes such as Cph1 from the cyanobacterium Synechocystis PCC 6803 are light-regulated histidine kinases in which the light signal is transferred from the N-terminal chromophore module to the C-terminal kinase module. In this study, purified recombinant Cph1 was subjected to limited proteolysis using trypsin and endoproteinase Glu-C (V8). Cleavage sites of chromopeptide fragments were determined by MALDI-TOF and micro-HPLC on-line with tandem mass spectrometry in an ion trap mass spectrometer. Trypsin produced three major chromopeptides, termed F1 (S56 to R520), F2 (T64 to R472), and F3 (L81 to R472). F1 was produced only in the far-red absorbing form Pfr within 15 min and remained stable up to >1 h; F2 and F3 were obtained in the red-light absorbing form Pr within ca. 5-10 min. When F1 was photoconverted to Pr in the presence of trypsin, this fragment degraded to F2 and F3 within 1-2 min. On size exclusion chromatography, F1 eluted as a dimer in the Pfr and as a monomer in the Pr form, whereas F2 and F3 behaved always as monomers, irrespective of the light conditions. These and other results are discussed in the context of light-dependent subunit interactions, in which amino acids 473-520 within the PHY domain are required for chromophore-module subunit interaction within the homodimer. V8 proteolysis yielded five major chromopeptides, F4 (T17 to N449), F5 (T17 to E335), F6 (T17 to E323), F7 (unknown sequence), and F8 (tentatively L121 to E323). F6 and F8 were formed in the Pr form, whereas F4, F5, and F7 were preferentially formed in the Pfr form. Three amino acids next to specific cleavage sites, R520, R472, and E323, were altered by site-directed mutagenesis. The mutants were analyzed by UV-vis spectroscopy, size exclusion chromatography, and autophosphorylation. Histidine kinase activity was low in R472A, R520P, and R520A; in all mutants, the ratio of phosphorylation intensity between Pr and Pfr was reduced. Thus, light regulation of autophosphorylation is negatively affected in all mutants. In R472P, E323P, and E323D, the phosphorylation intensity of the Pfr form exceeded that of the wild-type control. This result shows that the histidine kinase activity of Cph1 is actively inhibited by photoconversion into Pfr.
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PMID:Light-induced conformational changes of cyanobacterial phytochrome Cph1 probed by limited proteolysis and autophosphorylation. 1564 69

The deletion of a gene coding for a histidine kinase (sll0750, Hik8) in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 resulted in a conditional lethal phenotype with a pleiotropic effect on the expression of genes involved in glucose metabolism. This mutant had comparable doubling times to wild type (WT) in continuous-light-grown photoautotrophic and mixotrophic cultures, whereas it grew poorly under mixotrophic conditions with different light and dark cycles. Growth was completely stopped, and cells eventually died, when the light duration was less than 6 h on a 24-h regimen. Northern blot analysis demonstrated that steady-state transcript levels of genes encoding key enzymes of glycolysis, gluconeogenesis, the oxidative pentose phosphate pathway, and glycogen metabolism were significantly altered in a strain with mutant hik8 (Deltahik8) grown with or without glucose. In some cases, differential expression was dependent on growth conditions (photoautotrophic versus mixotrophic). The enzyme activities of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and phosphofructokinase were significantly reduced in Deltahik8 compared to WT. Glycogen determination indicated that Deltahik8 accumulated glycogen under mixotrophic conditions but was unable to utilize these reserves for heterotrophic growth. The results suggest that the loss of gap1 transcription in the absence of Hik8 was the key factor that rendered cells unable to catabolize glucose and grow heterotrophically. Additionally, the transcript levels of the phytochrome gene (cph1) and its cotranscribed response regulator gene (rcp1) were significantly reduced and its dark inducibility was lost in Deltahik8. The results demonstrated that Hik8 plays an important role in glucose metabolism and is necessary for heterotrophic growth.
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PMID:Pleiotropic effect of a histidine kinase on carbohydrate metabolism in Synechocystis sp. strain PCC 6803 and its requirement for heterotrophic growth. 1577 80

Although most two-component signal transduction systems use a simple phosphotransfer pathway from one histidine kinase (HK) to one response regulator (RR), a multiple-step phosphorelay involving a phosphotransfer scheme of His-Asp-His-Asp was also discovered. Central to this multiple-step-type signal transduction pathway are a hybrid-type HK, containing both an HK domain and an RR receiver domain in a single protein, and a histidine-containing phosphotransfer (HPT) that can exist either as a domain in hybrid-type HKs or as a separate protein. Although multiple-step phosphorelay systems are predominant in eukaryotes, it has been previously suggested that they are less common in prokaryotes. In this study, it was found that putative hybrid-type HKs were present in 56 of 156 complete prokaryotic genomes, indicating that multiple-step phosphorelay systems are more common in prokaryotes than previously appreciated. Large expansions of hybrid-type HKs were observed in 26 prokaryotic species, including photosynthetic cyanobacteria such as Nostoc sp. PCC 7120, and several pathogenic bacteria such as Coxiella burnetii. Phylogenetic analysis indicated that there was no common ancestor for hybrid-type HKs, and their origin and expansion was achieved by lateral recruitment of a receiver domain into an HK molecule and then duplication as one unit. Lateral recruitment of additional sensory domains such as PAS was also evident. HPT domains or proteins were identified in 32 of the genomes with hybrid-type HKs; however, no significant gene expansion was observed for HPTs even in a genome with a large number of hybrid-type HKs. In addition, fewer HPTs than hybrid-type HKs were identified in all prokaryotic genomes.
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PMID:Distribution and evolution of multiple-step phosphorelay in prokaryotes: lateral domain recruitment involved in the formation of hybrid-type histidine kinases. 1600 Jul 7

Cyanobacteria respond to nutrient stress conditions by degrading their light-harvesting complexes for photosynthesis, a process regulated in Synechococcus sp. PCC 7942 by the sensor histidine kinase non-bleaching sensor (NblS). In yeast two-hybrid screenings for proteins interacting with NblS we have identified a novel type of protein, named SipA for NblS interacting protein A. Specific binding between NblS and SipA is observed with both yeast and bacterial two-hybrid systems. Additional yeast two-hybrid screenings with SipA as bait further confirmed the specificity of the interaction and allowed us to map their determinants to the ATP-binding domain of NblS. Strong conservation and coevolution of both NblS and SipA in cyanobacteria further suggests the importance of SipA in the context of the NblS signal transduction network.
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PMID:SipA, a novel type of protein from Synechococcus sp. PCC 7942, binds to the kinase domain of NblS. 1645 Nov 77

In the cyanobacterium Synechococcus elongatus PCC 7942, circadian timing is transmitted from the KaiABC-based central oscillator to the transcription factor RpaA via the KaiC-interacting histidine kinase SasA to activate transcription, thereby generating rhythmic circadian gene expression. However, KaiC can also repress circadian gene expression, including its own. The mechanism and significance of this negative feedback regulation have been unclear. Here, we report a novel gene, labA (low-amplitude and bright), that is required for negative feedback regulation of KaiC. Disruption of labA abolished transcriptional repression caused by overexpression of KaiC and elevated the trough levels of circadian gene expression, resulting in a low-amplitude phenotype. In contrast, overexpression of labA significantly lowered circadian gene expression. Furthermore, genetic analysis indicated that labA and sasA function in parallel pathways to regulate kaiBC expression, whereas rpaA functions downstream from labA for kaiBC expression. These results suggest that temporal information from the KaiABC-based oscillator diverges into a LabA-dependent negative pathway and a SasA-dependent positive pathway, and then converges onto RpaA to generate robust circadian gene expression. It is likely that quantitative information of KaiC is transmitted to RpaA through LabA, whereas SasA mediates the state of the KaiABC-based oscillator.
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PMID:labA: a novel gene required for negative feedback regulation of the cyanobacterial circadian clock protein KaiC. 1721 Jul 89

The hybrid sensory histidine kinase Slr1759 of the cyanobacterium Synechocystis sp. strain PCC 6803 contains multiple sensory domains and a multi-step phosphorelay system. Immuno blot analysis provided evidence that the histidine kinase Slr1759 is associated with the cytoplasmic membrane. The gene slr1759 is part of an operon together with slr1760, encoding a response regulator. A comparative investigation was performed on Synechocystis sp. strain PCC 6803 wild type (WT) and an insertionally inactivated slr1759-mutant (Hik14) which also lacks the transcript for the response regulator Slr1760. The mutant Hik14 grew significantly slower than WT in the early growth phase, when both were inoculated with a low cell density into BG11 medium without additional buffer and when aerated with air enriched with 2% CO2. Since the aeration with CO2-enriched air results in a decrease of the pH value in the medium, the growth experiments indicated that Hik14 is not able to adjust its metabolic activities as rapidly as WT to compensate for a larger decrease of the pH value in the medium. No significant differences in growth between Hikl4 and WT were observed when cells were inoculated with a higher cell density in BG11 medium or when the BG11 medium contained 50 mM Epps-NaOH, pH 7.5, to prevent the pH drop. This Hik14 phenotype has so far only been seen under the above defined growth condition. Results of photosynthetic activity measurements as well as Northern blot-, immuno blot-, and metabolite analyses suggest that the two-component system Slr1759/Slr1760 has a function in the coordination of several metabolic activities which is in good agreement with the complex domain structure of Slr1759. The direct targets of this two-component system have so far not been identified.
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PMID:Physiological and molecular characterization of a Synechocystis sp. PCC 6803 mutant lacking histidine kinase Slr1759 and response regulator Slr1760. 1729 99

In photosynthetic organisms, sugar catabolic pathways, such as glycolysis and the oxidative pentose phosphate pathway, are indispensable for survival in the absence of light. In this review, we will focus on the regulation of sugar catabolic gene expression in cyanobacteria, especially that of Synechocystis sp. PCC 6803 (Synechocystis). In Synechocystis, the expression of sugar catabolic genes is activated by the shift from light-to-dark and diurnally during the evening, and positively regulated by a histidine kinase, Hik8, and a RNA polymerase sigma factor, SigE. Mutants for these regulators are defective for survival in the dark and unable to carry out light-activated heterotrophic growth. It has also been shown that transcripts of sugar catabolic genes are increased by nitrogen depletion and a global nitrogen regulator NtcA is essential for the induction. These results indicate a regulatory connection between nitrogen status and sugar catabolism in cyanobacteria.
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PMID:Sugar catabolism regulated by light- and nitrogen-status in the cyanobacterium Synechocystis sp. PCC 6803. 1748

The Pho regulon is controlled by the histidine kinase-response regulator pair SphS-SphR in many cyanobacteria and up-regulation of the Pho regulon can be monitored by measuring alkaline phosphatase activity. However, the mechanism regulating signal transduction between SphS and SphR has not been described. We have created a cyanobacterial strain allowing the introduction of mutations into the transmitter domain of SphS. Mutations at Thr-167, adjacent to the H motif of SphS, introduce elevated alkaline phosphatase activity in the presence of phosphate and an enhancement of alkaline phosphatase activity, when compared to the control strain, in phosphate-limiting media. SphU acts as a negative regulator of the SphS-SphR system in Synechocystis sp. PCC 6803 and we show that constitutive alkaline phosphatase activity in the absence of SphU requires signal transduction through SphS and SphR. However, constitutive activity in the absence of SphU is severely attenuated in the DeltaSphU:SphS-T167N mutant. Our data suggest that Thr-167 contributes to the mechanism underlying regulation by SphU. We have also assembled a deletion mutant system allowing the introduction of mutations into SphR and show that Gly-225 and Trp-236, which are both conserved in SphR from cyanobacteria, are essential for activation of the Pho regulon under phosphate-limiting conditions.
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PMID:Phosphate sensing in Synechocystis sp. PCC 6803: SphU and the SphS-SphR two-component regulatory system. 1754 76

In Synechocystis sp. PCC 6803 extracellular phosphate levels are relayed to the pho regulon via the SphS histidine kinase. In this cyanobacterium, the start codon of sphS has been assigned as a GUG, thereby predicting SphS to be a cytosolic protein lacking a putative N-terminal region found in the PhoR orthologue from Escherichia coli. Inspection upstream of sphS located an in-frame AUG positioned 47 codons in front of the putative GUG start. Alterations at either of the putative AUG or GUG start codons did not prevent transcription of sphS; however, up-regulation of alkaline phosphatase mRNA, or alkaline phosphatase activity, was not detected in response to phosphate-limiting conditions when the AUG was mutated. Alkaline phosphatase expression and activity serve as phenotypic markers for activation of the pho regulon. Therefore, the pho regulon had not been induced in these cells, whereas normal up-regulation was observed in strains carrying mutations at the GUG. These results show that the AUG codon, not the GUG codon, is the initiation site for sphS translation in Synechocystis sp. PCC 6803.
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PMID:Identification of the start codon for sphS encoding the phosphate-sensing histidine kinase in Synechocystis sp. PCC 6803. 1757 13


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