Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.26.3 (RNase III)
 1,015 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An Escherichia coli double strand specific endoribonuclease, RNase III, was cloned, expressed in large amounts, and purified to homogeneity. Enzyme activity was monitored by assaying fractions for the ability to correctly process exogenous RNA containing specific RNase III cleavage sites. DEAE-Sepharose ion exchange chromatography in the presence of a linear KCl gradient (from 0.02 M to 0.75 M) demonstrated that RNase III exists as two distinct forms. One form elutes at a KCl concentration of 0.13 M and the other elutes at 0.33 M. The presence of stoichiometric amounts of the GTP-binding protein Era during purification results in the conversion of the low salt form into the high salt form. Size exclusion chromatography demonstrated that both forms exist as a dimer in solution. In order to investigate the nature of the dimer, protein cross-linking was performed and cross-linked products were detected by silver staining. The protein-protein dimer can be visualized at protein:cross-linker molar ratios as low as 1:15 within 1 minute of exposure to cross-linker in 0.1 M KCl. Upon addition of substrate RNA to the cross-linking reaction a second form of the protein-protein dimer (with a slightly smaller apparent molecular weight) becomes prominent. Induction of the new form is absolutely dependent upon the addition of substrate mRNA to the reaction mixture. We postulate that the RNase III dimer undergoes a dramatic conformational change upon recognition of RNA which we are able to trap by cross-linking.
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PMID:Characterization of the biochemical properties of recombinant ribonuclease III. 169 24

The TnphoA-induced Bradyrhizobium japonicum mutant 184 shows slow growth and aberrant colonization of soybean nodules. Using a DNA fragment adjacent to the transposon insertion site as a probe, a 3.4-kb BglII fragment of B. japonicum 110spc4 DNA was identified and cloned. Sequence analysis indicated that two truncated ORFs and three complete ORFs were encoded on this fragment. A database search revealed homologies to several other prokaryotic proteins: PdxJ (an enzyme involved in vitamin B6 biosynthesis), AcpS (acyl carrier protein synthase), Lep or Sip (prokaryotic type I signal peptidase), RNase III (an endoribonuclease which processes double-stranded rRNA precursors and mRNA) and Era (a GTP-binding protein required for cell division). The mutation in strain 184 was found to lie within the signal peptidase gene, which was designated sipF. Therefore, sipF is located in a region that encodes gene products involved in posttranscriptional and posttranslational processing processes. By complementation of the lep(ts) E. coli mutant strain IT41 it was demonstrated that sipF indeed encodes a functional signal peptidase, and genetic complementation of B. japonicum mutant 184 by a 2.8-kb SalI fragment indicated that sipF is expressed from a promoter located directly upstream of sipF. Using a non-polar kanamycin resistance cassette, a specific sipF mutant was constructed which exhibited defects in symbiosis similar to those of the original mutant 184.
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PMID:A second gene for type I signal peptidase in Bradyrhizobium japonicum, sipF, is located near genes involved in RNA processing and cell division. 987 Jun 99