PubMed · 8610002
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
N A Ellis. 1996-05-09. Mutation-causing mutations.. https://doi.org/10.1038/381110a0
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
UAP56 (U2AF65 associated protein) is a member of the DEAD-box helicase family. Helicases are essential enzymes generally involved in the metabolism of nucleic acids. The gene encoding a member of DEAD-box family was cloned and characterized from the human malaria parasite Plasmodium falciparum. PfU52 is homologous to UAP56 and contains the RNA-dependent ATPase, RNA helicase and RNA binding activities. Using the parasite extract we report that PfU52 is involved in splicing reaction. Site-directed mutagenesis studies indicate that the conserved residues glycine 181, isoleucine 182 and arginine 206 are involved in RNA binding and this activity is required for the enzymatic activities of PfU52. PfU52 is expressed in all the intraerythrocytic developmental stages of the parasite. In the present study we have reported the detailed characterization of PfU52 from P. falciparum and these results advance the knowledge regarding the function of UAP56 in general.
Cysteine string protein (CSP) is a 34 kDa secretory vesicle protein bearing a "J-domain" as well as a palmitoylated cysteine-rich "string" region used for membrane attachment. Mutation of the CSP gene causes impaired presynaptic neuromuscular transmission in Drosophila melanogaster, implicating CSP as part of the exocytotic protein machinery. The J-domain of CSP shares homology with the universally conserved DnaJ family, a group of proteins that act as co-chaperones with Hsc70 and its homologs. Hsc70 is an abundant neural protein with coupled protein binding and ATPase activities. We have investigated the CSP modulation of Hsc70 ATPase activity. Here we demonstrated that CSP enhances Hsc70 ATPase activity in a dose-dependent manner. CSP activation of Hsc70 was maximal ( approximately 12 times) at 1:1 stoichiometry and above. We show that a J-domain-containing fragment (amino acids 1-82) of CSP is sufficient for the activation of Hsc70. Neither CSP nor the amino-terminal fragment stimulate the activity of the isolated Hsc70 ATPase domain (amino acids 1-386). CSP does not significantly increase the activity of N-ethylmaleimide-sensitive fusion protein, another ATPase required for transport vesicle function. Our results suggest that CSP, a DnaJ family member associated with the secretory vesicle cycle regulates Hsc70 functions. Hsc70 may function within the biochemical pathways of exo- and endocytosis to promote the formation or dissociation of multimeric complexes or to regulate conformational changes.
The ArsA ATPase is the catalytic subunit of the Ars pump that catalyzes arsenical extrusion in Escherichia coli, thus providing resistance. The active form of ArsA is a homodimer with four nucleotide binding sites, two from each monomer. The codons for Gly-15 in the N-terminal consensus nucleotide binding sequence and Gly-334 in the C-terminal sequence were individually mutated to cysteine codons. Cells expressing an arsAG334C mutation retained arsenite resistance, while an arsAG15C mutation resulted in substantial reductions in arsenite resistance, transport, and ATPase activity. Selection for suppression of the G15C mutation that restored arsenite resistance yielded an A344V substitution. Ala-344 is located adjacent to the C-terminal nucleotide binding sequence. The second site mutation did not suppress the loss of resistance resulting from G18D, G20S, or T22I substitutions in the N-terminal nucleotide binding site. Cells expressing the G15C/A344V double mutant regained arsenite extrusion. These results suggest a spatial proximity of Gly-15 and Ala-344 and support a model for interaction of the nucleotide binding sites in ArsA.