PubMed Health⌕ Search

Biomedical subjects

J M Pardo

Publications and source records attributed to J M Pardo.

28 records · Page 2Linked to original sources
PubMed1989

Structure of a plasma membrane H+-ATPase gene from the plant Arabidopsis thaliana.

Physiological and biochemical studies have suggested that the plant plasma membrane H+-ATPase controls many important aspects of plant physiology, including growth, development, nutrient transport, and stomata movements. We have started the genetic analysis of this enzyme by isolating both genomic and cDNA clones of an H+-ATPase gene from Arabidopsis thaliana. The cloned gene is interrupted by 15 introns, and there is partial conservation of exon boundaries with respect to animal (Na+/K+)- and Ca2+-ATPases. In general, the relationship between exons and the predicted secondary and transmembrane structure of different ATPases with phosphorylated intermediate support a somewhat degenerate correspondence between exons and structural modules. The predicted amino acid sequence of the plant H+-ATPase is more closely related to fungal and protozoan H+-ATPases than to bacterial K+-ATPases or to animal (Na+/K+)-, (H+/K+)-, and Ca2+-ATPases. There is evidence for the existence of at least three isoforms of the plant H+-ATPase gene. These results open the way for a molecular approach to the structure and function of the plant proton pump.

Amino Acid Sequence↗
PubMed1989

Biochemical characterization of two cloned resistance determinants encoding a paromomycin acetyltransferase and a paromomycin phosphotransferase from Streptomyces rimosus forma paromomycinus.

The mechanism conferring resistance to paromomycin in Streptomyces rimosus forma paromomycinus, the producing organism, was studied at the level of both protein synthesis and drug-inactivating enzymes. Ribosomes prepared from this organism grown in either production or nonproduction medium were fully sensitive to paromomycin. A paromomycin acetyltransferase and a paromomycin phosphotransferase, both characteristic of the producer, were highly purified from extracts prepared from two Streptomyces lividans transformants harboring the relevant genes inserted in pIJ702-derived plasmids. In vitro, paromomycin was inactivated by either activity. In vivo, however, S. lividans clones containing the gene for either enzyme inserted in the low-copy-number plasmid pIJ41 were resistant to only low levels of paromomycin. In contrast, an S. lividans transformant containing both genes inserted in the same pIJ41-derived plasmid displayed high levels of resistance to paromomycin. These results indicate that both genes are required to determine the high levels of resistance to this drug in the producing organism. Paromomycin is doubly modified by the enzymes. However, whereas acetylparomomycin was a poorer substrate than paromomycin for the phosphotransferase, phosphorylparomomycin was modified more actively than was the intact drug by the acetyltransferase. These findings are discussed in terms of both a permeability barrier to paromomycin and the possible role(s) of the two enzymes in the biosynthetic pathway of this antibiotic.

Acetyltransferases↗
PubMed1988

Similar short elements in the 5' regions of the STA2 and SGA genes from Saccharomyces cerevisiae.

The 5' region of the SGA and STA2 genes, encoding the intra- and extracellular glucoamylases, respectively, from Saccharomyces cerevisiae have been sequenced. In addition, the transcription initiation sites have been determined. Four distinct short elements (named I to IV) were found in both genes. Element III has the consensus sequence PuCATTTAPiG with a bilateral symmetry around the central T, and is present in both genes as a direct repeat. This motive seems responsible for the coregulation of STA2 and SGA by the repressor STA10 gene of S. cerevisiae.

Amino Acid Sequence↗
PubMed1987

Purification and characterization of a hygromycin B phosphotransferase from Streptomyces hygroscopicus.

A hygromycin B phosphotransferase activity from Streptomyces hygroscopicus has been highly purified by ammonium sulphate fractionation followed by affinity column chromatography through Sepharose-6B-hygromycin-B. The combined active fractions showed a single protein band (41 kDa) when subjected to polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. When gel electrophoresis was performed under non-denaturing conditions, the single protein band promoted in situ phosphorylation of hygromycin B, indicating that this protein corresponded to the purified hygromycin B phosphotransferase. The enzyme has been purified 236-fold and approximate Km values of 0.56 microM for hygromycin B and ATP, respectively, were deduced.

Kanamycin Kinase↗
PubMed1986

Cloning of the STA2 and SGA genes encoding glucoamylases in yeasts and regulation of their expression by the STA10 gene of Saccharomyces cerevisiae.

The Saccharomyces STA2 and SGA genes, encoding the extracellular and intracellular sporulation-specific glucoamylase respectively, have been cloned and their transcription and regulation studied. The STA2 gene differs from the SGA gene in that it contains an extra piece of DNA, which encodes the domain for exportation of the extracellular glucoamylase. The STA2 gene produces a single 2.85 kb transcript. Transcription of the SGA gene is initiated from two different sites, yielding two transcripts of 1.95 and 2.40 kb. Transcription of both STA2 and SGA genes is repressed by the STA10 gene of Saccharomyces cerevisiae.

Chromosome Mapping↗
PubMed1986

Virilization of a female infant due to an adrenal tumor.

We report here the case of a 22-month-old girl with virilization due to a potentially malignant adrenal tumor. She presented with clitoromegaly and growth of pubic hair, first noticed at birth. The clinical picture, hormonal profile, and pathologic findings are described. The practical aspects of the differential diagnosis and treatment are illustrated.

Adrenal Cortex Neoplasms↗
PubMed1985

Biochemical basis of resistance to hygromycin B in Streptomyces hygroscopicus--the producing organism.

Hygromycin B, an aminocyclitol antibiotic that strongly inhibits both 70S and 80S ribosomes, is synthesized by Streptomyces hygroscopicus. Ribosomes from this Gram-positive mycelial bacterium are inhibited in vitro by the antibiotic. In contrast, the streptomycete is highly resistant to the drug in vivo since it possesses hygromycin B phosphotransferase activity. This enzyme has been shown by gel filtration to have a molecular weight of 42000, and to modify its antibiotic substrate to produce 7"-O-phosphoryl-hygromycin B which totally lacks biological activity both in vivo and in vitro.

Acetyltransferases↗