Divalent cations can induce the exposure of GroEL hydrophobic surfaces and strengthen GroEL hydrophobic binding interactions. Novel effects of Zn2+ GroEL interactions

Bill T. Brazil, Jesse Ybarra, Paul M. Horowitz

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

Fluorescent and non-fluorescent probes have been used to show that divalent cations (Ca2+, Mg2+, Mn2+, and Zn2+) significantly increase hydrophobic exposure on GroEL, whereas monovalent cations (K+ and Na+) have little effect. Zn2+ always induced the largest amount of hydrophobic exposure on GroEL. By using a new method based on interactions of GroEL with octyl-Sepharose, it was demonstrated that Zn2+ binding strengthens GroEL hydrophobic binding interactions and increases the efficiency of substrate release upon the addition of MgATP and GroES. The binding of 4,4'-bis(1- anilino-8-naphthalenesulfonic acid) to GroEL in the presence of Zn2+ has a Kd ≃ 1 μM, which is similar to that observed previously for the GroEL 4,4'- bis(1-anilino-8-naphthalenesulfonic acid) complex. Urea denaturation, sedimentation velocity ultracentrifugation, and electron microscopy revealed that the quaternary structure of GroEL in the presence of Zn2+ had a stability and morphology equivalent to unliganded GroEL. In contrast, circular dichroism suggested some loss in both α-helical and β-sheet secondary structure in the presence of Zn2+. These data suggest that divalent cations can modulate the amount of hydrophobic surface presented by GroEL. Furthermore, the influence of Zn2+ on GroEL hydrophobic surface exposure as well as substrate binding and release appears to be distinct from the stabilizing effects of Mg2+ on GroEL quaternary structure.

Original languageEnglish (US)
Pages (from-to)3257-3263
Number of pages7
JournalJournal of Biological Chemistry
Volume273
Issue number6
DOIs
StatePublished - Feb 6 1998
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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