Papers by JOSE Lopez-coronado
Plant Physiology, May 1, 2000
Overexpression of the HAL1 gene in yeast has a positive effect on salt tolerance by maintaining a... more Overexpression of the HAL1 gene in yeast has a positive effect on salt tolerance by maintaining a high internal K+ concentration and decreasing intracellular Na+ during salt stress. In the present work, the yeast gene HAL1 was introduced into tomato (Lycopersicon esculentum Mill.) by Agrobacterium tumefaciens-mediated transformation. A sample of primary transformants was self-pollinated, and progeny from both transformed and non-transformed plants (controls) were evaluated for salt tolerance in vitro and in vivo. Results from different tests indicated a higher level of salt tolerance in the progeny of two different transgenic plants bearing four copies or one copy of the HAL1 gene. In addition, measurement of the intracellular K+ to Na+ ratios showed that transgenic lines were able to retain more K+ than the control under salt stress. Although plants and yeast cannot be compared in an absolute sense, these results indicate that the mechanism controlling the positive effect of the HAL1 gene on salt tolerance may be similar in transgenic plants and yeast.
FEBS Letters, 2000
Phosphatases converting 3P P-phosphoadenosine 5P Pphosphate (PAP) into adenosine 5P P-phosphate a... more Phosphatases converting 3P P-phosphoadenosine 5P Pphosphate (PAP) into adenosine 5P P-phosphate are of fundamental importance in living cells as the accumulation of PAP is toxic to several cellular systems. These enzymes are lithium-sensitive and we have characterized a human PAP phosphatase as a potential target of lithium therapy. A cDNA encoding a human enzyme was identified by data base screening, expressed in Escherichia coli and the 33 kDa protein purified to homogeneity. The enzyme exhibits high affinity for PAP (K m 6 6 1 W WM) and is sensitive to subtherapeutic concentrations of lithium (IC 50 = 0.3 mM). The human enzyme also hydrolyzes inositol-1,4-bisphosphate with high affinity (K m = 0.4 W WM), therefore it can be considered as a dual specificity enzyme with high affinity (W WM range) for both PAP and inositol-1,4-bisphosphate. Hydrolysis of inositol-1,4bisphosphate was also inhibited by lithium (IC 50 = 0.6 mM). Thus, we present experimental evidence for a novel target of lithium therapy, which could explain some of the side effects of this therapy.
Plant Journal, Feb 1, 1999
The yeast HAL2 gene encodes a lithium-and sodiumsensitive phosphatase that hydrolyses 3Ј-phosphoa... more The yeast HAL2 gene encodes a lithium-and sodiumsensitive phosphatase that hydrolyses 3Ј-phosphoadenosine-5Ј-phosphate (PAP). Salt toxicity in yeast results from Hal2 inhibition and accumulation of PAP, which inhibits sulphate assimilation and RNA processing. We have investigated whether the model plant Arabidopsis thaliana contains sodium-sensitive PAP phosphatases. The Arabidopsis HAL2-like gene family is composed of three members: AtAHL and AtSAL2, characterized in the present work, and the previously identified AtSAL1. The AtAHL and AtSAL2 cDNAs complement the auxotrophy for methionine of the yeast hal2 mutant and the recombinant proteins catalyse the conversion of PAP to AMP in a Mg 2⍣dependent reaction sensitive to inhibition by Ca 2⍣ and Li ⍣. The PAP phosphatase activity of AtAHL is sensitive to physiological concentrations of Na ⍣ , whereas the activities of AtSAL1 and AtSAL2 are not. Another important difference is that AtAHL is very specific for PAP while AtSAL1 and AtSAL2 also act as inositol polyphosphate 1-phosphatases. AtAHL constitutes a novel type of sodium-sensitive PAP phosphatase which could act co-ordinately with plant sulphotransferases and serve as target of salt toxicity in plants.
Journal of Biological Chemistry, Jun 1, 1999
We report the molecular cloning in Rattus norvegicus of a novel mammalian enzyme (RnPIP), which s... more We report the molecular cloning in Rattus norvegicus of a novel mammalian enzyme (RnPIP), which shows both 3-phosphoadenosine 5-phosphate (PAP) phosphatase and inositol-polyphosphate 1-phosphatase activities. This enzyme is the first PAP phosphatase characterized at the molecular level in mammals, and it represents the first member of a novel family of dual specificity enzymes. The phosphatase activity is strictly dependent on Mg 2؉ , and it is inhibited by Ca 2؉ and Li ؉ ions. Lithium chloride inhibits the hydrolysis of both PAP and inositol-1,4-bisphosphate at submillimolar concentration; therefore, it is possible that the inhibition of the human homologue of RnPIP by lithium ions is related to the pharmacological action of lithium. We propose that the PAP phosphatase activity of RnPIP is crucial for the function of enzymes sensitive to inhibition by PAP, such as sulfotransferase and RNA processing enzymes. Finally, an unexpected connection between PAP and inositol-1,4-bisphosphate metabolism emerges from this work.
Applied and Environmental Microbiology, Dec 1, 2002
Cork taint is a musty or moldy off-odor in wine mainly caused by 2,4,6-trichloroanisole (2,4,6-TC... more Cork taint is a musty or moldy off-odor in wine mainly caused by 2,4,6-trichloroanisole (2,4,6-TCA). We examined the role of 14 fungal strains isolated from cork samples in the production of 2,4,6-TCA by O methylation of 2,4,6-trichlorophenol (2,4,6-TCP). The fungal strains isolated belong to the genera Penicillium (four isolates); Trichoderma (two isolates); and Acremonium, Chrysonilia, Cladosporium, Fusarium, Mortierella, Mucor, Paecilomyces, and Verticillium (one isolate each). Eleven of these strains could produce 2,4,6-TCA when they were grown directly on cork in the presence of 2,4,6-TCP. The highest levels of bioconversion were carried out by the Trichoderma and Fusarium strains. One strain of Trichoderma longibrachiatum could also efficiently produce 2,4,6-TCA in liquid medium. However, no detectable levels of 2,4,6-TCA production by this strain could be detected on cork when putative precursors other than 2,4,6-TCP, including several anisoles, dichlorophenols, trichlorophenols, or other highly chlorinated compounds, were tested. Time course expression studies with liquid cultures showed that the formation of 2,4,6-TCA was not affected by a high concentration of glucose (2% or 111 mM) or by ammonium salts at concentrations up to 60 mM. In T. longibrachiatum the O methylation of 2,4,6-TCP was catalyzed by a mycelium-associated S-adenosyl-L-methionine (SAM)-dependent methyltransferase that was strongly induced by 2,4,6-TCP. The reaction was inhibited by S-adenosyl-Lhomocysteine, an inhibitor of SAM-dependent methylation, suggesting that SAM is the natural methyl donor. These findings increase our understanding of the mechanism underlying the origin of 2,4,6-TCA on cork, which is poorly understood despite its great economic importance for the wine industry, and they could also help us improve our knowledge about the biodegradation and detoxification processes associated with chlorinated phenols.
The Plant Journal, 1999
The yeast HAL2 gene encodes a lithium-and sodiumsensitive phosphatase that hydrolyses 3Ј-phosphoa... more The yeast HAL2 gene encodes a lithium-and sodiumsensitive phosphatase that hydrolyses 3Ј-phosphoadenosine-5Ј-phosphate (PAP). Salt toxicity in yeast results from Hal2 inhibition and accumulation of PAP, which inhibits sulphate assimilation and RNA processing. We have investigated whether the model plant Arabidopsis thaliana contains sodium-sensitive PAP phosphatases. The Arabidopsis HAL2-like gene family is composed of three members: AtAHL and AtSAL2, characterized in the present work, and the previously identified AtSAL1. The AtAHL and AtSAL2 cDNAs complement the auxotrophy for methionine of the yeast hal2 mutant and the recombinant proteins catalyse the conversion of PAP to AMP in a Mg 2⍣dependent reaction sensitive to inhibition by Ca 2⍣ and Li ⍣. The PAP phosphatase activity of AtAHL is sensitive to physiological concentrations of Na ⍣ , whereas the activities of AtSAL1 and AtSAL2 are not. Another important difference is that AtAHL is very specific for PAP while AtSAL1 and AtSAL2 also act as inositol polyphosphate 1-phosphatases. AtAHL constitutes a novel type of sodium-sensitive PAP phosphatase which could act co-ordinately with plant sulphotransferases and serve as target of salt toxicity in plants.
Zenodo (CERN European Organization for Nuclear Research), Jan 9, 2023
Practice that could be integrated into planned trans-RI competence centres.
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Papers by JOSE Lopez-coronado