Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.27.1 (RNase)
 16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The in vitro reconstitution of tobacco mosaic virus (TMV) is initiated by the binding of a disk of TMV protein to the 'disk recognition site', a region of the RNA chain at or near the 5'-terminus for which the disk has special affinity. In order to gain insight into the recognition process, we have studied the ability of disks to encapsidate short RNA fragments produced by partial pancreatic or T1 RNase digestion of TMV RNA. The disk is capable of dicriminating among such fragments, encapsidating only a few of the many present in the digest. The products of encapsidation are short nucleoprotein rods of the same diameter as TMV and of length proportional to that of the encapsidated RNA fragment. The particles differ from TMV, however, in one significant aspect (apart from their length): they possess rings of RNA-free protein at one or both extremities of the rod. In the case of T1 RNase digestion the principal encapsidated fragments were fragments T1 (105 nucleotides) and a family of smaller fragments containing elements of the same sequence. Partial digestion with pancreatic RNase generated only one major fragment (fragment P1; 150 nucleotides) with affinity for the disk. Fragment T1 has been sequenced and shown to represent a portion of the coat protein cistron. Fragment P1 has been partially sequenced but its function is not yet known. Several lines of evidence indicate that fragment T1 is not the disk recognition site. The portion of the TMV RNA chain from which fragment P1 is derived, on the other hand, is encapsidated early in the reconstitution process; thus fragment P1 may contain the disk recognition site. Fragment T1 and fragment P1 both have purine-rich and cytosine-poor sequences near their termini. In addition, fragment T1, and possibly fragment P1, possess a periodicity of order three in purine residues. It seems likely that one or both of the aforesaid properties are largely responsible for the affinity of these fragments for the disk.
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PMID:Specific encapsidation of fragments of TMV RNA. 1 30

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