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)

Two new polarity suppressors (Su27 and Su78) have been isolated in Escherichia coli. Both suppress polarity in the trp and lac operons, and neither shows codon specificity for suppression. Extreme polar mutants of the lac z gene that contain either Su27 or Su78 make mRNA from the entire operon; however, no active beta-galactosidase is translated from the z-gene messenger, and the amount of distal messenger is greater than would be expected from corresponding enzyme activities. Puromycin treatment of lac(+) strains mimics the effect of polar chain-termination mutations in destabilizing lac mRNA. This effect is completely reversed by Su27, and it is partially reversed by Su78. The results suggest that these suppressors act by stabilizing mRNA after premature termination of protein synthesis.
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PMID:New polarity suppressors in Escherichia coli: suppression and messenger RNA stability. 494 49

Moses, V. (University of California, Berkeley), and M. Calvin. Lifetime of bacterial messenger ribonucleic acid. J. Bacteriol. 90:1205-1217. 1965.-When cells from a stationary culture of Escherichia coli were placed in fresh medium containing inducer for beta-galactosidase, growth, as represented by increase in turbidity and by total protein synthesis, started within 30 sec. By contrast, beta-galactosidase synthesis was greatly delayed compared with induction during exponential growth. Two other inducible enzymes (d-serine deaminase and l-tryptophanase) and one repressible enzyme (alkaline phosphatase) showed similar lags. The lags were not due to catabolite repression. They could not be reduced by pretreatment of the culture with inducer, or by supplementing the fresh medium with amino acids or nucleotides. The lag was also demonstrated by an i(-) mutant constitutive for beta-galactosidase synthesis. An inhibitor of ribonucleic acid (RNA) synthesis, 6-azauracil, preferentially inhibited beta-galactosidase synthesis compared with growth in both inducible and constitutive strains. Puromycin, an inhibitor of protein synthesis, acted as an inhibitor at additional sites during the induction of beta-galactosidase synthesis. No inhibition of the reactions proceeding during the first 20 sec of induction was observed, but puromycin seemed to prevent the accumulation of messenger RNA during the period between 20 sec and the first appearance of enzyme activity after 3 min. It is suggested that these observations, together with many reports in the literature that inducible enzyme synthesis is more sensitive than total growth to some inhibitors and adverse growth conditions, can be explained by supposing that messenger RNA for normally inducible enzymes is biologically more labile than that for some normally constitutive proteins. The possible implications of this hypothesis for the achievement of cell differentiation by genetic regulation of enzyme synthesis are briefly discussed.
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PMID:Lifetime of bacterial messenger ribonucleic acid. 532 76

The type D simian retroviruses cause immunosuppression in macaques and have been reported as a presumptive opportunistic infection in a patient with AIDS. Previous evidence based on viral interference has strongly suggested that the type D simian viruses share a common but unknown cell surface receptor with three type C viruses: feline endogenous virus (RD114), baboon endogenous virus, and avian reticuloendotheliosis virus. Furthermore, the receptor gene for these viruses has been mapped to human chromosome 19q13.1-13.2. We now report the isolation and characterization of a cell surface receptor for this group of retroviruses by using a human T-lymphocyte cDNA library in a retroviral vector. Swiss mouse fibroblasts (NIH 3T3), which are naturally resistant to RD114, were transduced with the retroviral library and then challenged with an RD114-pseudotyped virus containing a dominant selectable gene for puromycin resistance. Puromycin selection yielded 12 cellular clones that were highly susceptible to a beta-galactosidase-encoding lacZ(RD114) pseudotype virus. Using PCR primers specific for vector sequences, we amplified a common 2.9-kb product from 10 positive clones. Expression of the 2.9-kb cDNA in Chinese hamster ovary cells conferred susceptibility to RD114, baboon endogenous virus, and the type D simian retroviruses. The 2.9-kb cDNA predicted a protein of 541 amino acids that had 98% identity with the previously cloned human Na+-dependent neutral-amino-acid transporter Bo. Accordingly, expression of the RD114 receptor in NIH 3T3 cells resulted in enhanced cellular uptake of L-[3H]alanine and L-[3H]glutamine. RNA blot (Northern) analysis suggested that the RD114 receptor is widely expressed in human tissues and cell lines, including hematopoietic cells. The human Bo transporter gene has been previously mapped to 19q13.3, which is closely linked to the gene locus of the RD114 receptor.
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PMID:A sodium-dependent neutral-amino-acid transporter mediates infections of feline and baboon endogenous retroviruses and simian type D retroviruses. 1019 49