Thermodynamic Characterization of Interactions between Ornithine Transcarbamylase Leader Peptide and Phospholipid Bilayer Membranes

Melanie Myers, Jennifer Emtage, Ernesto I Freire, Obdulio L. Mayorga

Research output: Contribution to journalArticle

Abstract

The interactions of the targeting sequence of the mitochondrial enzyme ornithine transcarbamylase with phospholipid bilayers of different molecular compositions have been studied by high-sensitivity heating and cooling differential scanning calorimetry, high-sensitivity isothermal titration calorimetry, fluorescence spectroscopy, and electron microscopy. These studies indicate that the leader peptide interacts strongly with dipalmitoylphosphatidylcholine (DPPC) bilayer membranes containing small mole percents of the anionic phospholipids dipalmitoylphosphatidylglycerol (DPPG) or brain phosphatidylserine (brain PS) but not with pure phosphatidylcholines. For the first time, the energetics of the leader peptide-membrane interaction have been measured directly by using calorimetric techniques. At 20 °C, the association of the peptide with the membrane is exothermic and characterized by an association constant of 2.3 X 106M-Iin the case of phosphatidylglycerol-containing and 0.35 X 106M-1in the case of phosphatidylserine-containing phospholipid bilayers. In both cases, the enthalpy of association is -60 kcal/mol of peptide. Additional experiments using fluorescence techniques suggest that the peptide does not penetrate deeply into the hydrophobic core of the membrane. The addition of the leader peptide to DPPC/DPPG (5:1) or DPPC/brain PS (5:1) small sonicated vesicles results in vesicle fusion. The fusion process is dependent on peptide concentration and is maximal at the phase transition temperature of the vesicles and minimal at temperatures below the phase transition.

Original languageEnglish (US)
Pages (from-to)4309-4315
Number of pages7
JournalBiochemistry
Volume26
Issue number14
DOIs
StatePublished - 1987

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Ornithine Carbamoyltransferase
Protein Sorting Signals
Thermodynamics
1,2-Dipalmitoylphosphatidylcholine
Phosphatidylserines
Phospholipids
Membranes
Peptides
Phase Transition
Association reactions
Brain
Fusion reactions
Phase transitions
Phosphatidylglycerols
Calorimetry
Transition Temperature
Fluorescence Spectrometry
Differential Scanning Calorimetry
Fluorescence spectroscopy
Phosphatidylcholines

ASJC Scopus subject areas

  • Biochemistry

Cite this

Thermodynamic Characterization of Interactions between Ornithine Transcarbamylase Leader Peptide and Phospholipid Bilayer Membranes. / Myers, Melanie; Emtage, Jennifer; Freire, Ernesto I; Mayorga, Obdulio L.

In: Biochemistry, Vol. 26, No. 14, 1987, p. 4309-4315.

Research output: Contribution to journalArticle

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