Analysis of the perturbation of phospholipid model membranes by rhodanese and its presequence

G. Zardeneta, P. M. Horowitz

Research output: Contribution to journalArticlepeer-review

24 Scopus citations

Abstract

The ability of the cytoplasmically synthesized mitochondrial enzyme rhodanese and its putative import signal sequence to interact with model phospholipid membranes was characterized. Membrane perturbation assays were used to test a current hypothesis that the initial step in protein translocation may involve binding of signal sequences with membrane lipids. Here we show comparative studies on the effect of native and various forms of denatured rhodanese, as well as two peptides, rho(1-23) and rho(11-23), derived from its NH2-terminal sequence, on the perturbation of 6- carboxyfluorescein-containing large unilamellar vesicles composed of either cardiolipin, phosphatidylcholine, or phosphatidylserine. We monitored the degree of perturbation by measuring dye leakage and found differential perturbation by either peptide or protein. Unfolded rhodanese perturbed vesicles in the order phosphatidylserine > cardiolipin >> phosphatidylcholine. Denatured rhodanese was ~25 times more effective (on a molar basis) than rho(1-23) in the disruption of anionic liposomes. Rho(11- 23) was unable to perturb liposomes. We found an inverse correlation between degree of activity of rhodanese folding intermediates and their ability to perturb liposomes. On urea denaturation, enzymatic activity was completely lost before membrane perturbation ability reached significant levels. Analysis of the peptides by circular dichroism showed that anionic liposomes can induce α-helical structure only in rho(1-23) and denatured rhodanese. Intrinsic peptide fluorescence studies showed that only rho(1-23) and denatured rhodanese partitioned into these model membranes. Results obtained here imply that peptides from naturally occurring α-helical structures may need adjacent motifs for helical structure induction in lipid environments, and the subsequent secondary structure may, in turn, promote partitioning of these segments into the lipid phase and ultimately lead to membrane perturbation.

Original languageEnglish (US)
Pages (from-to)24193-24198
Number of pages6
JournalJournal of Biological Chemistry
Volume267
Issue number34
StatePublished - 1992
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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