Nucleotides reveal polynucleotide phosphorylase activity from conventionally purified GroEL

Jesse Ybarra, Paul M. Horowitz

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


GroEL, as conventionally purified, can be incubated with nucleotides to produce high molecular weight material with an absorption maximum at 260 nm. This material is most clearly demonstrated when samples are subjected to gel filtration under conditions where GroEL is monomeric. There is a time- dependent increase in the high molecular weight material that occurs on incubation with ADP or, more slowly, with ATP. This material is generated during incubation, and none is present in the initial samples. Experiments with nucleases, proteases, radiolabeled nucleotides, and chemical cleavage reagents demonstrate that the high molecular weight material is polyadenylic acid whose formation is inhibited by phosphate. These results are consistent with the GroEL samples containing polynucleotide phosphorylase activity. Nondenaturing gels stained with acridine orange, after incubation in ADP, reveal that the activity producing the poly(A) coelectrophoreses with authentic polynucleotide phosphorylase. Conditions that remove the tryptophan-like fluorescence from preparations of GroEL also remove the PNPase activity. Thus, this activity is not associated with GroEL itself. The results are consistent with reports that GroEL can associate with RNase E and with other studies showing that RNase E and PNPase can form complexes. Thus, the present experiments support suggestions that GroEL can participate in multiprotein complexes that are involved in mRNA processing and degradation.

Original languageEnglish (US)
Pages (from-to)25063-25066
Number of pages4
JournalJournal of Biological Chemistry
Issue number41
StatePublished - 1996
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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