Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several approaches were used to study the role of GroEL, the prototype chaperonin, in the nitrogen fixation (nif) system. An Escherichia coli groEL mutant transformed with the Klebsiella pneumoniae nif gene cluster accumulated very low to nondetectable levels of nitrogenase components compared with the isogenic wild-type strain or the mutant cotransformed with the wild-type groE operon. In K. pneumoniae, overexpression of the E. coli groE operon markedly accelerated the rate of appearance of the MoFe protein and its constituent polypeptides after the start of derepression. The groEL mutation in E. coli decreased NifA-dependent beta-galactosidase expression from the nifH promoter but did not affect the constitutive expression of nifA from the tet promoter of ntr-controlled expression from the nifLA promoter. The possibility that GroEL is required for the correct folding of NifA was supported by coimmunoprecipitation of NifA with anti-GroEL antibodies. Kinetic analyses of nitrogenase assembly in 35S pulse-chased K. pneumoniae pointed to the existence of high-molecular-weight intermediates in MoFe protein assembly and demonstrated the transient binding of newly synthesized NifH and NifDK to GroEL. Overall, these results indicate that GroEL fulfills both regulatory and structural functions in the nif system.
 ...
PMID:Involvement of GroEL in nif gene regulation and nitrogenase assembly. 168 Aug 48

A study was performed to characterize DNA fragment No. 17 of C. psittaci strain P-1041 which encoded 42 KD beta-galactosidase fusion protein with type-specific antigenicity. Sequence determination identified a partial open reading frame that spanned about 1,200b. p. nucleotides. Screening the literatures for the nucleotide and deduced amino acid sequences revealed extensive similarity between the DNA fragment of P-1041 and two chlamydial hypB genes. This DNA showed 91.5% homology with C. psittaci GPIC hypB gene in nucleotide sequence and 96.4% homology in deduced amino acid sequence. The hypB gene of C. trachomatis serovar A and the P-1041 DNA fragment showed 81.2% and 91.3% homology in nucleotide and amino acid sequences, respectively. Dot enzyme-linked immunosorbent assay, for the products of deleted DNA fragments defined the coding region for type-specific antigenic polypeptide. In addition, the P-1041 DNA fragment carried a sequence highly homologous (greater than 49%) with other bacterial and plant genes called chaperonin which responds to various stress in cells. From these results, the P-1041 DNA fragment was found to be a part of hypB gene and to encode the region critical for type-specific antigenicity.
 ...
PMID:Characterization of DNA fragment from Chlamydia psittaci avian strain which shows high homology with hypB gene of Chlamydia. 182 39

We have studied the effect of the components of the GroE molecular chaperone machine on the refolding of the Escherichia coli enzyme beta-galactosidase, a tetrameric protein whose 116-kDa promoters should not completely fit within the central cavity of the GroEL toroid. In the absence of other additives, GroEL formed a weak complex with chemically denatured beta-galactosidase, reduced its propensity to aggregate, and increased the recovery yields of active enzyme twofold without altering its folding pathway. When present together with the chaperonin, ATP--and to a lesser extent AMP-PNP--reduced the recovery yields and led to the resumption of aggregation. The use of the complete chaperonin system (GroEL, GroES, and ATP) eliminated the GroEL-mediated increase in recovery and folding proceeded less efficiently than in buffer alone. This unusual behavior can be explained in terms of a chaperonin "buffering" effect and the different affinities of GroE complexes for denatured beta-galactosidase.
 ...
PMID:Influence of the GroE molecular chaperone machine on the in vitro refolding of Escherichia coli beta-galactosidase. 886 84

A large number of bacteria regulate chaperone gene expression by the CIRCE-HrcA system in which a DNA element called CIRCE serves as binding site for the repressor protein HrcA under non-heat-shock conditions. We have cloned the two consecutive genes hrcA and grpE of Bradyrhizobium japonicum by using a complementation approach that screened for GrpE function. In vivo and in vitro transcript mapping demonstrated that both genes are transcribed separately from RpoH (sigma(32))-dependent promoters. To investigate the supposed negative regulatory function of HrcA, we compared the expression of putative target genes in the wild type with that in an hrcA mutant. Transcription of the CIRCE-associated chaperonin operons groESL(4) and groESL(5), as well as the beta-galactosidase activity derived from corresponding groE-lacZ fusions, was strongly elevated in the hrcA mutant even at physiological temperatures. Expression of other heat shock regulons (RpoH or ROSE dependent) was not affected. To study the activity of HrcA in vitro, we purified a histidine-tagged version of the protein under nondenaturing conditions. Specific binding to the CIRCE element was obtained with a soluble fraction of HrcA in gel retardation experiments.
 ...
PMID:Role of HrcA and CIRCE in the heat shock regulatory network of Bradyrhizobium japonicum. 1061 57

Sulfolobus solfataricus has developed into an important model organism for molecular and biochemical studies of hyperthermophilic archaea. Although a number of in vitro systems have been established for the organism, efficient tools for genetic manipulations have not yet been available for any hyperthermophile. In this work, we have developed a stable and selectable shuttle vector based on the virus SSV1 of Sulfolobus shibatae. We have introduced pUC18 for propagation in Escherichia coli and the genes pyrEF coding for orotidine-5'-monophosphate pyrophosphorylase and orotidine-5'-monophosphate decarboxylase of Sulfolobus solfataricus as selectable marker to complement pyrimidine auxotrophic mutants. Furthermore, the beta-galactosidase gene (lacS) was introduced into this vector as a reporter under the control of the strong and heat-inducible promoter of the Sulfolobus chaperonin (thermosome). After transformation of a S. solfataricus pyrEF/lacS double mutant, the vector was found to reside as a single-copy vector, stably integrated into the host chromosome via the site-specific recombination system of SSV1. Specific beta-galactosidase activities in transformants were found to be fourfold higher than in wild-type S. solfataricus cells, and increased to more than 10-fold after heat shock. Greatly increased levels of lacS mRNA were detected in Northern analyses, demonstrating that this reporter gene system is suitable for the study of regulated promoters in Sulfolobus and that the vector can also be used for the high-level expression of genes from hyperthermophilic archaea.
 ...
PMID:A reporter gene system for the hyperthermophilic archaeon Sulfolobus solfataricus based on a selectable and integrative shuttle vector. 1278 52

'Pseudomonas butanovora' uses an alcohol-inducible alkane monooxygenase (BMO) to grow on C(2)-C(9) n-alkanes. Five ORFs were identified flanking the BMO structural genes. Two of the ORFs, bmoR, encoding a putative sigma(54)-transcriptional regulator BmoR, and bmoG, encoding a putative GroEL chaperonin BmoG, were analysed by gene-inactivation experiments. The BmoR-deficient mutant grew at slower growth rates than the wild-type on C(2)-C(5) n-alkanes and showed little to no growth on C(6)-C(8) n-alkanes within 7 days. A BmoR-deficient mutant was constructed in the 'P. butanovora' bmoX : : lacZ reporter strain and used to test whether bmoR was involved in bmoX induction after growth on C(2)-C(8) carbon sources. In acetate- or lactate-grown cells, C(2)-C(8) n-alcohols failed to induce beta-galactosidase activity. In contrast, in propionate-, butyrate- or pentanoate-grown cells, n-butanol induced approximately 45 % of the beta-galactosidase activity observed in the control bmoX : : lacZ strain. In propionate-grown cells, C(2)-C(5) n-alcohols induced beta-galactosidase activity, whereas C(7) and C(8) n-alcohols did not. BmoR may act as a sigma(54)-transcriptional regulator of bmo that is controlled by the n-alcohol produced in the alkane oxidation. During growth on short-chain-length fatty acids, however, another BMO regulatory system seems to be activated to promote transcription of bmo by short-chain-length alcohols (i.e. </=C(6)). The bmoG-deficient mutant did not grow on C(2)-C(8) n-alkanes; however, it was capable of transcribing bmoX and bmoC of the BMO operon. BmoG may act as a chaperonin to assemble competent BMO.
 ...
PMID:Involvement of BmoR and BmoG in n-alkane metabolism in 'Pseudomonas butanovora'. 1817 33