Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The rat nephron displays two ouabain-sensitive K-ATPases: one, which is present in proximal tubules and thick ascending limbs of normal rats, is specifically activated by K+ and is down-regulated by K+ depletion, whereas the other one appears in collecting ducts of K+-depleted rats and is activated by either Na+ or K+. To determine which of these two ATPases is similar to colonic-type H,K-ATPase, we quantitated by reverse transcriptase-polymerase chain reaction (RT-PCR) the mRNAs encoding the colonic H,K-ATPase alpha subunit in microdissected nephron segments. In normal rats, statistically significant amounts of colonic H,K-ATPase mRNAs were detected exclusively in cortical thick ascending limbs and cortical collecting ducts (200-500 copies/mm). Because these levels of expression were low (1-1.2 copies/target cell), they probably have no physiological relevance. In rats fed a K+-depleted diet for 2 weeks, expression of colonic H,K-ATPase was markedly enhanced in cortical and medullary collecting ducts (5000-12,000 copies/mm or 30-40 copies per cell), whereas it remained low in all other nephron segments. Thus, colonic H,K-ATPase alpha subunit is specifically expressed in cortical and outer medullary collecting ducts of K+-depleted rats where it likely accounts for the ouabain-sensitive K-ATPase activity.
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PMID:Quantitative RT-PCR analysis of mRNAs encoding a colonic putative H, K-ATPase alpha subunit along the rat nephron: effect of K+ depletion. 876 9

The P-type ATPases (e.g., Na+-K+-ATPase and Ca2+-ATPase) occur widely in living cells of fungi, Protozoa, plants, and animals. These ion pumps show a high degree of divergence in their primary structures but share a limited number of common amino acid residues for their ATP-catalytic function. Particularly, the amino acid sequences for the phosphorylation site (DKTGTLT) and the binding site for ATP (and its analogs; GDGVND) are conserved throughout evolution. Using two degenerate oligonucleotides corresponding to these regions, we applied a polymerase chain reaction (PCR) technique to the search for P-type ATPase isoforms, which will provide a clue to the evolutionary mechanisms of ion pumps in Tetrahymena thermophila. A total of 12 distinct P-type ATPase genes were identified. Sequence comparisons revealed that seven of them can be compiled into a multigene family, which is similar to animal Na+-K+- and H+-K+-ATPase genes. One of them is close to the sarco(endo)plasmic reticulum Ca2+-ATPase gene, and the other four share a significant homology with the gene encoding Plasmodium ATPase-1 whose function is unknown. A Northern blot analysis and reverse transcriptase-PCR demonstrated that all identified genes are expressed, but the expression levels vary widely under different culture conditions. A Southern blot analysis after pulse-field gel electrophoresis showed that all of these genes exist in T. thermophila macronuclei. The Na+-K+- and H+-K+-ATPase gene family has a high multiplicity (at least 10 different genes detected on genomic Southern blot analysis) and is distributed on four different macronuclear chromosomes. On the basis of a calculation with the amino acid sequences of the cloned cytoplasmic loop region (between the phosphorylation and the gamma-[4-(N-2-chloroethyl-N-methylamino)]-benzylamido ATP sites), the genes with >80% identity form a cognate linkage group within the same macronuclei chromosome, whereas the genes with <70% identity are separated in different chromosomes. The phylogenetic analysis showed that this multigene family is the result of a series of gene duplications.
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PMID:Primary structure and evolution of the ATP-binding domains of the P-type ATPases in Tetrahymena thermophila. 912 16