Activation of phospholipase C δ1 through C2 domain by a Ca2+-enzyme- phosphatidylserine ternary complex

Jon W. Lomasney, Hwei Fang Cheng, Steve R. Roffler, Klim King*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

65 Scopus citations

Abstract

The concentration of free Ca2+ and the composition of nonsubstrate phospholipids profoundly affect the activity of phospholipase C δ1 (PLCδ1). The rate of PLCδ1 hydrolysis of phosphatidylinositol 4,5-bisphosphate was stimulated-20-fold-by phosphatidylserine (PS), 4-fold by phosphatidic acid (PA), and not at all by phosphatidylethanolamine or phosphatidylcholine (PC). PS reduced the Ca2+ concentration required for half-maximal activation of PLCδ1 from 5.4 to 0.5μM. In the presence of Ca2+, PLCδ1 specifically bound to PS/PC but not to PA/PC vesicles in a dose-dependent and saturable manner. Ca2+ also bound to PLCδ1 and required the presence of PS/PC vesicles but not PA/PC vesicles. The free Ca2+ concentration required for half-maximal Ca2+ binding was estimated to be 8 μM. Surface dilution kinetic analysis revealed that the K(m) was reduced 20-fold by the presence of 25 mol % PS, whereas V(max) and K(d) were unaffected. Deletion of amino acid residues 646654 from the C2 domain of PLCδ1 impaired Ca2+ binding and reduced its stimulation and binding by PS. Taken together, the results suggest that the formation of an enzyme-Ca2+-PS ternary complex through the C2 domain increases the affinity for substrate and consequently leads to enzyme activation.

Original languageEnglish (US)
Pages (from-to)21995-22001
Number of pages7
JournalJournal of Biological Chemistry
Volume274
Issue number31
DOIs
StatePublished - Jul 30 1999

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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