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

Comparison of growth rates of isogenic strains that synthesize varying levels of beta-galactosidase during continuous culture on non-inducing medium indicates that synthesis of low levels of non-functional protein has a small but possibly significant effect upon growth rate.
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PMID:Selective disadvantage of non-functional protein synthesis in Escherichia coli. 79 67

The construction and use of a Tn3-lac transposon, Tn3-HoHo1, is described. Tn3-HoHo1 can serve as a transposon mutagen and provides a new and useful system for the random generation of both transcriptional and translational lacZ gene fusions. In these fusions the production of beta-galactosidase, the lacZ gene product, is placed under the control of the gene into which Tn3-HoHo1 has inserted. The expression of the gene can thus be analyzed by monitoring beta-galactosidase activity. Tn3-HoHo1 carries a non-functional transposase gene; consequently, it can transpose only if transposase activity is supplied in trans, and is stable in the absence of this activity. A system for the insertion of Tn3-HoHo1 into sequences specifically contained within plasmids is described. The applicability of Tn3-HoHo1 was demonstrated studying three functional regions of the Agrobacterium tumefaciens A6 Ti plasmid. These regions code for octopine catabolism, virulence and plant tumor phenotype. The regulated expression of genes contained within each of these regions was analyzed in Agrobacterium employing Tn3-HoHo1 generated lac fusions.
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PMID:A Tn3 lacZ transposon for the random generation of beta-galactosidase gene fusions: application to the analysis of gene expression in Agrobacterium. 299 Sep 12

The activity in vivo of HIV-1 proteinase (PR) was analysed in the baculovirus expression system, using eight different constructs of the prt gene under the control of polyhedrin (PH) promoters of various strengths. None of the active PRs was expressed in substantial quantities, and only PH-fused and/or non-functional PR mutants accumulated in high amounts in insect cells. However, enough PR activity was generated from a lengthened PR construct in insect cells to process Gag polyprotein substrate co-expressed in the same cells in trans. Fusion of the first 58 residues from the PH sequence to the PR N terminus did not significantly change its activity and specificity of cleavage of the Gag substrate. When analysed under mild denaturing conditions, PH-fused or unfused full-length PR point mutants, as well as PH-fused or unfused C-terminal deletion mutants, showed a propensity to multimerize, with a predominant occurrence of dimers. The incorporation of PR into Gag particles was studied using eight Gag-PR fusion constructs, all containing a non-functional PR mutant. The PR domain was fused to the C-terminal p6 domain of Gag (p6gag), or translated in frame with NCp7 (as in frameshifted Gag-Pol polyprotein) and followed by downstream sequences of increasing lengths from the Pol domain or the bacterial beta-galactosidase. The results suggested that the presence of the p6gag domain was detrimental to the encapsidation of polyprotein-embedded PR.
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PMID:Proteolytic activity in vivo and encapsidation of recombinant human immunodeficiency virus type 1 proteinase expressed in baculovirus-infected cells. 901 Feb 96

As serious side effects affected recent virus-mediated gene transfer studies, novel vectors with improved safety profiles are urgently needed. In the present study, replication-deficient retroviral vectors based on feline foamy virus (FFV) were constructed and analyzed. The novel FFV vectors are devoid of almost the complete env gene plus the internal promoter - accessory bel gene cassette including the gene for the viral transcriptional transactivator Bel1/Tas. In these Bel1/Tas-independent vectors, expression of the lacZ (beta-galactosidase) marker gene is directed by the heterologous, constitutively active human ubiquitin C promoter (ubi). Env-transcomplemented vectors have un-concentrated titers of more than 10(5) transducing units/ml. The vectors allow efficient transduction of a broad array of diverse target cells, which can be increased by repeated vector exposure. However, the number of lacZ marker gene expressing cells decreased slightly upon serial passages of the transduced cells. Vectors carrying a self-inactivating (SIN) deletion of the TATA box and most parts of the viral promoter were not rescued by wt FFV whereas those with the intact or a partially deleted promoter were readily reactivated. This finding indicates that the viral promoters are in fact non-functional, pointing to a highly advantageous safety profile of these new FFV-ubi-lacZ-SIN vectors.
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PMID:Construction and characterization of efficient, stable and safe replication-deficient foamy virus vectors. 1720 7

The vast majority of proteins functions in complex with one or more of the same or other proteins, indicating that protein-protein interactions play crucial roles in biology. Here, we present a beta-galactosidase reconstitution-based bacterial two-hybrid system in which two proteins of interest are fused to two non-functional but complementing beta-galactosidase truncations (Delta alpha and Delta omega). The level of complemented beta-galactosidase activity, driven by the protein-protein recognition between both non-beta-galactosidase parts of the chimeras, reflects whether or not the proteins of interest interact. Our approach was validated by reconfirming some well-established Escherichia coli cytoplasmic and membranous interactions, including well-chosen mutants, and providing the first in vivo evidence for the transient periplasmic interaction between Rhodobacter capsulatus cytochrome c2 and cytochrome c peroxidase. We demonstrated the major advantages of this in vivo two-hybrid technique: i) analyses of interactions are not limited to particular cellular compartments, ii) the potential of using the system in mutation-driven structure-function studies, and iii) the possibility of its application to transiently interacting proteins. These benefits demonstrate the relevance of the method as a powerful new tool in the broad spectrum of interaction assessment methods.
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PMID:A beta-galactosidase-based bacterial two-hybrid system to assess protein-protein interactions in the correct cellular environment. 1753 72

The unintended consequences of gene targeting in mouse models have not been thoroughly studied and a more systematic analysis is needed to understand the frequency and characteristics of off-target effects. Using RNA-seq, we evaluated targeted and neighboring gene expression in tissues from 44 homozygous mutants compared with C57BL/6N control mice. Two allele types were evaluated: 15 targeted trap mutations (TRAP); and 29 deletion alleles (DEL), usually a deletion between the translational start and the 3' UTR. Both targeting strategies insert a bacterial beta-galactosidase reporter (LacZ) and a neomycin resistance selection cassette. Evaluating transcription of genes in +/- 500 kb of flanking DNA around the targeted gene, we found up-regulated genes more frequently around DEL compared with TRAP alleles, however the frequency of alleles with local down-regulated genes flanking DEL and TRAP targets was similar. Down-regulated genes around both DEL and TRAP targets were found at a higher frequency than expected from a genome-wide survey. However, only around DEL targets were up-regulated genes found with a significantly higher frequency compared with genome-wide sampling. Transcriptome analysis confirms targeting in 97% of DEL alleles, but in only 47% of TRAP alleles probably due to non-functional splice variants, and some splicing around the gene trap. Local effects on gene expression are likely due to a number of factors including compensatory regulation, loss or disruption of intragenic regulatory elements, the exogenous promoter in the neo selection cassette, removal of insulating DNA in the DEL mutants, and local silencing due to disruption of normal chromatin organization or presence of exogenous DNA. An understanding of local position effects is important for understanding and interpreting any phenotype attributed to targeted gene mutations, or to spontaneous indels.
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PMID:Transcriptome Analysis of Targeted Mouse Mutations Reveals the Topography of Local Changes in Gene Expression. 2683 65