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)

A high-copy plasmid, pGA217, which carries a deletion (lacking the carboxy-terminal 20 amino acids) of the structural gene for ribosomal protein L10 (rplJ) is lethal to the cell in the absence of the gene (rplL) for r-proteins L7/L12, but only if the upstream operon for r-proteins L11 (rplK) and L1 (rplA) is present on the same plasmid. Measurements of beta-galactosidase activity of a hybrid protein expressed by a rplL-lacZ fusion indicated that the L10 fragment peptide which lacks the carboxy-terminal 20 amino acids is capable of exerting feedback regulation. Double transformation experiments with two compatible plasmids showed that the detrimental effect of the rplJ deletion on pGA217 can be reversed by the addition of a second plasmid which carries a functional gene for L7/L12. These two pieces of evidence suggest that the lethal effect of pGA217 is due to its property of feeding back on L7/L12 production from the chromosomal rplK gene. The upstream rplKA operon was inferred to have a cis-acting, stimulating effect on rplJ expression from the following evidence: (1) donor plasmids carrying the genes for L11 and/or L1 fail to exert a trans-acting effect, (2) deletion mutants which removed portions of rplK and/or rplA, but maintained the rplKA promoter, rplKp, still retained a severe growth-inhibiting effect. We suggest that these results can be explained by assuming that there is transcription from the rplKA promoter through rplJ and perhaps beyond.
 ...
PMID:The lethal effect of a plasmid resulting from transcriptional readthrough of rplJ from the rplKA operon in Escherichia coli. 634 92

A derivative of bacteriophage lambda, lambda 21, has been constructed and used for the cloning of Escherichia coli DNA fragments carrying promoters. Phage lambda 21 lacks the lac promoter operator and can accept DNA fragments up to 9.8 kilobases in size at a unique HindIII restriction endonuclease site adjacent to lacZ. Recombinant phage that carry promoters are readily identified by their expression of lacZ. Lysogens of these phages in strains harboring a deletion of the chromosomal lac operon are capable of growth on lactose as sole carbon source and can be used to study some of the regulatory signals that act upon the cloned promoter. In principle, lambda 21 can be used to clone any promoter DNA sequence with HindIII termini. PJ, the primary promoter for the rplJL-rpoBC operon, and P beta, a weak promoter for rpoBC, have been cloned in lambda 21. Transcription of lacZ from PJ was found to be subjected to feedback control by ribosomal protein L10 and to a lesser extent by ribosomal protein L7/L12. This suggests a possible L10-binding site near PJ that regulates transcription from that promoter. Lysogens of the phage that carries P beta responded to two regulatory signals: a rho-sensitive termination site preceding rpoBC and induction of beta-galactosidase synthesis by rifampicin. This suggests that P beta is a bona fide promoter for rpoBC.
 ...
PMID:Bacteriophage lambda vehicle for the direct cloning of Escherichia coli promoter DNA sequences: feedback regulation of the rplJL-rpoBC operon. 644 64