Disease relevance of rph

• A recent X-ray crystallographic study of the polynucleotide phosphorylase (PNPase) from Streptomyces antibioticus reveals, for the first time, the atomic structure of a member of the RNase PH superfamily [1].
• The Ski6p/Rrp41p protein has homology to the Escherichia coli 3' to 5' exoribonuclease RNase PH, and both the Ski6p/Rrp41p and Rrp4p proteins are components of a multiprotein complex, termed the exosome, that contains at least three polypeptides with 3' to 5' exoribonuclease activities [2].
• Identification of the rph (RNase PH) gene of Bacillus subtilis: evidence for suppression of cold-sensitive mutations in Escherichia coli [3].

High impact information on rph

• An analysis of its amino acid sequence shows that the protein is composed of two core domains related to RNase PH, two RNA binding domains (KH and S1), and an alpha-helical domain [4].
• Although both PNPase and RNase PH act in a phosphorolytic manner, they differ substantially in size and substrate specificity [5].
• OrfE/RNase PH contains helix-turn-helix motifs resembling those in DNA-binding proteins, and it binds nonspecifically to DNA [6].
• The highly purified protein catalyzes the phosphorolytic cleavage of poly(A) at a rate of 1.6 mumol/min/mg and the formation of CDP from tRNA-CCA-Cn and orthophosphate at a rate equal to 0.14 mumol/min/mg, as characteristic for RNase PH [6].
• To obtain information about the function of this enzyme in vivo, the Escherichia coli rph gene encoding RNase PH was interrupted with either a kanamycin resistance or a chloramphenicol resistance cassette and transferred to the chromosome of a variety of RNase-resistant strains [7].

Chemical compound and disease context of rph

• RNase PH from extracts of Escherichia coli was purified to homogeneity and subjected to NH2-terminal sequencing [8].

Biological context of rph

• The equilibrium constant for RNase PH is near unity, suggesting that at the phosphate concentration present in vivo, the enzyme would participate in RNA degradation [9].
• Here we show that the RNase PH-negative, PNP-negative double-mutant strain actually displays a reversible cold-sensitive phenotype and that tRNA biosynthesis is normal [10].

Anatomical context of rph

• These data indicate that RNase PH and PNPase play an essential role that affects ribosome metabolism and that this function cannot be taken over by any of the hydrolytic exoribonucleases present in the cell [10].

Analytical, diagnostic and therapeutic context of rph

• Higher order multimers of RNase PH could be detected by gel filtration at higher protein concentrations and by protein cross-linking [9].

References