Literature summary for 3.1.26.3 extracted from

Saramago, M.; Robledo, M.; Matos, R.; Jimenez-Zurdo, J.; Arraiano, C.
Sinorhizobium meliloti RNase III catalytic features and impact on symbiosis (2018), Front. Genet., 9, 350 .

Cloned(Commentary)

Cloned (Comment)	Organism
gene rnc, DNA and amino acid sequence determination and analysis, sequence comparisons and phylogenetic tree, recombinant expression of His-tagged wild-type and mutant enzymes in Escherichia coli strain BL21(DE3) recArnc105. This strain, carrying an RNase III mutation, is used because it blocks the autoregulation of SmRNase III by the endogenous Escherichia coli homolog, resulting in a higher yield of the enzyme upon overexpression	Sinorhizobium meliloti

Cloned (Comment)

Organism

gene rnc, DNA and amino acid sequence determination and analysis, sequence comparisons and phylogenetic tree, recombinant expression of His-tagged wild-type and mutant enzymes in Escherichia coli strain BL21(DE3) recArnc105. This strain, carrying an RNase III mutation, is used because it blocks the autoregulation of SmRNase III by the endogenous Escherichia coli homolog, resulting in a higher yield of the enzyme upon overexpression

Sinorhizobium meliloti

Protein Variants

Protein Variants	Comment	Organism
E125A	site-directed mutagenesis, the mutation does not compromise wild-type enzyme SmRNase III dimerization ability	Sinorhizobium meliloti
E125Q	site-directed mutagenesis, mutation does not compromise wild-type enzyme SmRNase III dimerization ability	Sinorhizobium meliloti
additional information	an enzyme deletion mutant SmDELTArnc shows a symbiotic phenotype. Plants inoculated with the wild-type and complemented strains developed significantly longer shoots than those inoculated with the mutant bacteria, SmDELTArnc or SmDELTArnc (pSRK), which are similar to those of the control mock-treated plants	Sinorhizobium meliloti

Inhibitors

Inhibitors	Comment	Organism	Structure
Mn2+	activates at 0.1-50 mM, inhibitory at 100 mM	Sinorhizobium meliloti

Metals/Ions

Metals/Ions	Comment	Organism
Mg2+	activates, required	Sinorhizobium meliloti
Mn2+	activates, required, best metal ion at 0.1-50 mM, inhibitory at 100 mM	Sinorhizobium meliloti
additional information	Ca2+ does not likely support enzyme activity. Strictly metal cofactor-dependent activity of SmRNase III on the model R1.1 substrate	Sinorhizobium meliloti

Natural Substrates/ Products (Substrates)

Natural Substrates	Organism	Comment (Nat. Sub.)	Natural Products	Comment (Nat. Pro.)	Rev.	Reac.
additional information	Sinorhizobium meliloti	enzyme SmRNase III is double-strand specific and exhibits different preference for endogenous RNA substrates	?	-	?

Organism

Organism	UniProt	Comment	Textmining
Sinorhizobium meliloti	Q92R47	i.e. Ensifer meliloti or Sinorhizobium meliloti	-

Purification (Commentary)

Purification (Comment)	Organism
recombinant His-tagged wild-type and mutant enzymes from Escherichia coli strain BL21(DE3)recArnc105 by nickel affinity chromatography and gel filtration	Sinorhizobium meliloti

Substrates and Products (Substrate)

Substrates	Comment Substrates	Organism	Products	Comment (Products)	Rev.	Reac.
additional information	enzyme SmRNase III is double-strand specific and exhibits different preference for endogenous RNA substrates	Sinorhizobium meliloti	?	-	?
R1.1 RNA + H2O	R1.1 is a structured 60 nucleotides (nt)-long RNA molecule containing an asymmetric (4 nt/5 nt) internal loop, and it comes from the phage T7 early region between genes 1.0 and 1.1. This RNA contains an RNase III primary cleavage site (a) that is recognized in vivo and in vitro, and a secondary site (b) that is cleaved only in vitro. RNase III is known to cleave R1.1 at these two preferred sites (a and b) in a metal cofactor-dependent manner. Strictly metal cofactor-dependent activity of SmRNase III on the model R1.1 substrate	Sinorhizobium meliloti	?	-	?

Synonyms

Synonyms	Comment	Organism
RNase III	-	Sinorhizobium meliloti
RNase III-like protein	-	Sinorhizobium meliloti
rnc	-	Sinorhizobium meliloti
SmRNase III	-	Sinorhizobium meliloti

Temperature Optimum [°C]

Temperature Optimum [°C]	Temperature Optimum Maximum [°C]	Comment	Organism
37	-	assay at	Sinorhizobium meliloti

pH Optimum

pH Optimum Minimum	pH Optimum Maximum	Comment	Organism
8	-	assay at	Sinorhizobium meliloti

General Information

General Information	Comment	Organism
evolution	members of the ribonuclease (RNase) III family of enzymes are metal-dependent double-strand specific endoribonucleases. They are ubiquitously found and eukaryotic RNase III-like enzymes include Dicer and Drosha, involved in RNA processing and RNA interference. SmRNase III is a typical double-strand specific endoribonuclease, but with a minimal substrate length requirement different from that of its enterobacterial orthologue	Sinorhizobium meliloti
malfunction	SmRNase III loss-of-function neither compromises viability nor alters morphology of Sinorhizobium meliloti cells, but influences growth, nodulation kinetics, the onset of nitrogen fixation and the overall symbiotic efficiency of this bacterium on the roots of its legume host, alfalfa, which ultimately affects plant growth. Appearance of pink nodules. Symbiotic phenotype of the SmDELTArnc mutant	Sinorhizobium meliloti
additional information	probably a major role of the ultraconserved E125 amino acid in the metal-dependent catalysis mediated by enzyme SmRNase III	Sinorhizobium meliloti
physiological function	SmRNase III degrades endogenous RNA substrates of diverse biogenesis with different efficiency, and is involved in the maturation of the 23S rRNA. Impact of SmRNase III on nodulation and symbiotic nitrogen fixation in plants. Enzyme SmRNase III influences free-living growth and symbiotic performance of Sinorhizobium meliloti on alfalfa roots	Sinorhizobium meliloti