Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0162871 (abdominal aortic aneurysm)
 8,664 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To define the requirements for the homotypic fusion of mammalian endoplasmic reticulum (ER) membranes, we have developed a quantitative in vitro enzyme-linked immunosorbent assay. This assay measures the formation of IgG (H2L2) following the fusion of ER microsomes containing either the heavy or light chain subunits. Guanine nucleotide dissociation inhibitor (GDI), a protein that extracts Rab GTPases in the GDP-bound form from membranes, potently inhibits fusion. Inhibition was not observed using GDI mutants defective in Rab binding. Kinetic analysis of the inhibitory effects of GDI revealed that Rab activation is required immediately preceding or coincident with fusion and that this step is preceded by a priming event requiring a member of the AAA ATPase family. Our results suggest that homotypic fusion of ER membranes requires Rab and that Rab activation is a transient event necessary for the formation of a fusion pore leading to the mixing of luminal contents of ER microsomes.
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PMID:A Rab GTPase is required for homotypic assembly of the endoplasmic reticulum. 915 91

McrBC from Escherichia coli K-12 is a restriction enzyme that belongs to the family of AAA(+) proteins and cuts DNA containing modified cytosines. Two proteins are expressed from the mcrB gene: a full-length version, McrB(L), and a short version, McrB(S). McrB(L) binds specifically to the methylated recognition site and is, therefore, the DNA-binding moiety of the McrBC endonuclease. McrB(S) is devoid of DNA-binding activity. We observed that the quaternary structure of the endonuclease depends on binding of the cofactors. In gel filtration experiments, McrB(L) and McrB(S) form high molecular weight oligomers in the presence of Mg(2+) and GTP, GDP or GTP-gamma-S. Oligomerization did not require the presence of DNA and was independent of GTP hydrolysis. Electron micrographs of negatively stained McrB(L) and McrB(S) revealed ring-shaped particles with a central channel. Mass analysis by scanning transmission electron microscopy indicates that McrB(L) and McrB(S) form single heptameric rings as well as tetradecamers. In the presence of McrC, a subunit that is essential for DNA cleavage, the tetradecameric species was the major form of the endonuclease.
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PMID:The McrBC restriction endonuclease assembles into a ring structure in the presence of G nucleotides. 1140 97

Uridine 34 (U34) at the wobble position of the tRNA anticodon is post-transcriptionally modified, usually to mcm5s2, mcm5, or mnm5. The lack of the mcm5 or s2 modification at U34 of tRNALys, tRNAGlu, and tRNAGln causes ribosome pausing at the respective codons in yeast. The pauses occur during the elongation step, but the mechanism that triggers ribosome pausing is not known. Here, we show how the s2 modification in yeast tRNALys affects mRNA decoding and tRNA-mRNA translocation. Using real-time kinetic analysis we show that mcm5-modified tRNALys lacking the s2 group has a lower affinity of binding to the cognate codon and is more efficiently rejected than the fully modified tRNALys. The lack of the s2 modification also slows down the rearrangements in the ribosome-EF-Tu-GDP-Pi-Lys-tRNALys complex following GTP hydrolysis by EF-Tu. Finally, tRNA-mRNA translocation is slower with the s2-deficient tRNALys. These observations explain the observed ribosome pausing at AAA codons during translation and demonstrate how the s2 modification helps to ensure the optimal translation rates that maintain proteome homeostasis of the cell.
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PMID:Thio-Modification of tRNA at the Wobble Position as Regulator of the Kinetics of Decoding and Translocation on the Ribosome. 2836 83

Microtubules are non-covalent dynamic polymers essential for the life of all eukaryotic cells. Their dynamic behavior is regulated by a large array of cellular effectors. In vitro microtubule assays have been instrumental in dissecting the mechanism of microtubule-associated proteins. In this chapter, we focus on microtubule-severing enzymes katanin and spastin. They are AAA ATPases that generate internal breaks in microtubules by extracting tubulin dimers out of the microtubule lattice. We present protocols for TIRF microscopy-based assays that were instrumental in proving that these enzymes not only sever microtubules but also remodel the microtubule lattice by promoting the exchange of lattice GDP-tubulin with GTP-tubulin from the soluble pool. This activity can modulate microtubule dynamics and support microtubule-dependent microtubule amplification in the absence of a nucleating factor.
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PMID:In Vitro Reconstitution Assays of Microtubule Amplification and Lattice Repair by the Microtubule-Severing Enzymes Katanin and Spastin. 3187 96