Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.26.9 (ribonuclease)
 6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Eukaryotic 5S rRNA hybridizes specifically with 18S rRNA in vitro to form a stable intermolecular RNA:RNA hybrid. We have used 5S rRNA/18S rRNA fragment hybridization studies coupled with ribonuclease digestion and primer extension/chain termination analysis of 5S rRNA:18S rRNA hybrids to more completely map those mouse 5S rRNA and 18S rRNA sequences responsible for duplex formation. Fragment hybridization analysis has defined a 5'-terminal region of 5S rRNA (nucleotides 6-27) which base-pairs with two independent sequences in 18S rRNA designated Regions 1 (nucleotides 1157-1180) and 2 (nucleotides 1324-1339). Ribonuclease digestion of isolated 5S rRNA:18S rRNA hybrids with both single-strand- and double-strand-specific nucleases supports the involvement of this 5'-terminal 5S rRNA sequence in 18S rRNA hybridization. Primer extension/chain termination analysis of isolated 5S rRNA:18S rRNA hybrids confirms the base-pairing of 5S rRNA to the designated Regions 1 and 2 of 18S rRNA. Using these results, 5S rRNA:18S rRNA intermolecular hybrid structures are proposed. Comparative sequence analysis revealed the conservation of these hybrid structures in higher eukaryotes and the same but smaller core hybrid structures in lower eukaryotes and prokaryotes. This suggests that the 5S rRNA:16S/18S rRNA hybrids have been conserved in evolution for ribosome function.
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PMID:Intermolecular hybridization of 5S rRNA with 18S rRNA: identification of a 5'-terminally-located nucleotide sequence in mouse 5S rRNA which base-pairs with two specific complementary sequences in 18S rRNA. 170 45

Bacteriophage R17 RNA was labelled with (32)P and was subjected to partial digestion with ribonuclease T(1). The products were fractionated by ionophoresis on polyacrylamide gel. Two fragments were purified and their nucleotide sequences determined by methods involving complete and further partial digestion with ribonucleases A and T(1). Fragment 20 had a sequence that coded for the amino acids in positions 32-53 of the coat protein of the bacteriophage. Fragment 20X, on further purification in 7m-urea, gave rise to two smaller nucleotides whose sequences coded for the amino acids in positions 56-66 and 67-76 of the coat protein. The sequence of the two fragments was such that they could be written in the form of loops stabilized by base-pairing.
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PMID:Nucleotide sequences of two fragments from the coat-protein cistron of bacteriophage R17 ribonucleic acid. 456 95

Stretches of residual structure in the unfolded states of proteins could possibly constitute crucial regions that initiate protein folding. We are searching for such regions in barnase by dividing it into fragments. By this means, we can search for regions that just form within local sequences. We are also employing methods that can detect low levels of residual structure. In this study, we examine the fragment 1-22 and a large fragment (23-110) that contains all of the catalytic residues. Fragment 1-22 contains the first alpha-helix, and fragment 23-110 contains the second alpha-helix and beta-sheet structure-forming residues of native barnase. These fragments bind together rapidly and tightly upon association to form a fully native-like complex. Studies by circular dichroism and fluorescence spectroscopy indicate that each fragment is mainly disordered. However, we find by a procedure of titration with trifluoroethanol that about 3% of fragment 1-22 is helical in water at 25 degrees C. Importantly, we have detected residual catalytic activity in fragment 23-110 toward GpUp and RNA and the ability to bind the polypeptide inhibitor of barnase, barstar, suggesting that this fragment can form a native-like conformation in water. The catalytic activity does not result from a small amount of contaminating impurity of parent enzyme or other ribonuclease, since the activity requires a 1:1 mole ratio of fragment to barstar for complete inhibition, and the activity is lost in much lower concentrations of urea than are required to denature the parent enzyme. There is a very weak signal in the near-UV CD spectrum of the large fragment.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Folding of barnase in parts. 814 79