Identification and characterization of a high-affinity zinc uptake system inNeisseria gonorrhoeae

The uptake, internalization and intracellular degradation of 125I-labeled rt-PA (125I-rt-PA) by isolated rat hepatocytes was investigated. Incubation at 37°C resulted in internalization of 125I-rt-PA, followed by the appearance of labeled trichloroacetic acid-soluble (TCA) material in the inclubation media due to degradation of rt-PA. Degradation of rt-PA was inhibited by the presence of NH4Cl (10mM) or chloroquine (ImM) (lysosoma tropic agents) in the incubation media. This suggests that rt-PA degradation occurs intracellularly, perhaps within the lysosomes. 125I-rt-PA was taken up by rat hepatocytes through a specific, high affinity mechanism. Scatchard analysis of the data indicated that 106 molecules of rt-PA were taken up per cell/hour and the calculated dissociation constant was lOnM. Uptake of 125I-rt-PA was not inhibited by glycopeptides isolated from rt-PA nor by several other glycoproteins known to be cleared by identified hepatic receptors. These results suggest that the uptake of rt-PA by rat hepatocytes involves a receptor specific for t-PA and is not mediated by a carbohydrate specific receptor.

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Identification and characterization of high affinity antisense PNAs for the human unr (upstream of N-ras) mRNA which is uniquely overexpressed in MCF-7 breast cancer cells

Nucleic Acids Research ◽

10.1093/nar/gki968 ◽

2005 ◽

Vol 33 (21) ◽

pp. 6700-6711 ◽

Cited By ~ 8

Author(s):

H. Fang

Keyword(s):

Breast Cancer ◽

Cancer Cells ◽

Breast Cancer Cells ◽

High Affinity ◽

Identification And Characterization ◽

Mcf 7

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Characterization of Cadmium Uptake in Lactobacillus plantarum and Isolation of Cadmium and Manganese Uptake Mutants

Applied and Environmental Microbiology ◽

10.1128/aem.65.11.4741-4745.1999 ◽

1999 ◽

Vol 65 (11) ◽

pp. 4741-4745 ◽

Cited By ~ 26

Author(s):

Zhiqi Hao ◽

Heinz R. Reiske ◽

David B. Wilson

Keyword(s):

Lactobacillus Plantarum ◽

Chemical Mutagenesis ◽

Uptake System ◽

High Affinity ◽

Manganese Uptake ◽

Type Rate ◽

Wild Type Rate ◽

Dry Cell

ABSTRACT Two different Cd2+ uptake systems were identified inLactobacillus plantarum. One is a high-affinity, high-velocity Mn2+ uptake system which also takes up Cd2+ and is induced by Mn2+ starvation. The calculated Km and V maxare 0.26 μM and 3.6 μmol g of dry cell−1min−1, respectively. Unlike Mn2+ uptake, which is facilitated by citrate and related tricarboxylic acids, Cd2+ uptake is weakly inhibited by citrate. Cd2+ and Mn2+ are competitive inhibitors of each other, and the affinity of the system for Cd2+ is higher than that for Mn2+. The other Cd2+uptake system is expressed in Mn2+-sufficient cells, and noKm can be calculated for it because uptake is nonsaturable. Mn2+ does not compete for transport through this system, nor does any other tested cation, i.e., Zn2+, Cu2+, Co2+, Mg2+, Ca2+, Fe2+, or Ni2+. Both systems require energy, since uncouplers completely inhibit their activities. Two Mn2+-dependent L. plantarum mutants were isolated by chemical mutagenesis and ampicillin enrichment. They required more than 5,000 times as much Mn2+ for growth as the parental strain. Mn2+ starvation-induced Cd2+ uptake in both mutants was less than 5% the wild-type rate. The low level of long-term Mn2+ or Cd2+accumulation by the mutant strains also shows that the mutations eliminate the high-affinity Mn2+ and Cd2+uptake system.

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Two Plant Bacteria, S. meliloti and Ca. Liberibacter asiaticus, Share Functional znuABC Homologues That Encode for a High Affinity Zinc Uptake System

PLoS ONE ◽

10.1371/journal.pone.0037340 ◽

2012 ◽

Vol 7 (5) ◽

pp. e37340 ◽

Cited By ~ 25

Author(s):

Cheryl M. Vahling-Armstrong ◽

Huasong Zhou ◽

Lesley Benyon ◽

J. Kent Morgan ◽

Yongping Duan

Keyword(s):

Zinc Uptake ◽

Uptake System ◽

High Affinity ◽

Liberibacter Asiaticus

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Two Zinc Uptake Systems Contribute to the Full Virulence of Listeria monocytogenes during GrowthIn VitroandIn Vivo

Infection and Immunity ◽

10.1128/iai.05904-11 ◽

2011 ◽

Vol 80 (1) ◽

pp. 14-21 ◽

Cited By ~ 39

Author(s):

David Corbett ◽

Jiahui Wang ◽

Stephanie Schuler ◽

Gloria Lopez-Castejon ◽

Sarah Glenn ◽

...

Keyword(s):

Listeria Monocytogenes ◽

Zinc Uptake ◽

Detectable Effect ◽

Intracellular Growth ◽

Content Type ◽

Zinc Sensing ◽

Identification And Characterization ◽

Cell Deletion

ABSTRACTWe report here the identification and characterization of two zinc uptake systems, ZurAM and ZinABC, in the intracellular pathogenListeria monocytogenes. Transcription of both operons was zinc responsive and regulated by the zinc-sensing repressor Zur. Deletion of eitherzurAMorzinAhad no detectable effect on growth in defined media, but a doublezurAM zinAmutant was unable to grow in the absence of zinc supplementation. Deletion ofzinAhad no detectable effect on intracellular growth in HeLa epithelial cells. In contrast, growth of thezurAMmutant was significantly impaired in these cells, indicating the importance of the ZurAM system during intracellular growth. Notably, the deletion of bothzinAandzurAMseverely attenuated intracellular growth, with the double mutant being defective in actin-based motility and unable to spread from cell to cell. Deletion of eitherzurAMorzinAhad a significant effect on virulence in an oral mouse model, indicating that both zinc uptake systems are importantin vivoand establishing the importance of zinc acquisition during infection byL. monocytogenes. The presence of two zinc uptake systems may offer a mechanism by whichL. monocytogenescan respond to zinc deficiency within a variety of environments and during different stages of infection, with each system making distinct contributions under different stress conditions.

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