Purification of recombinant human cPLA2 gamma and identification of C-terminal farnesylation, proteolytic processing, and carboxymethylation by MALDI-TOF-TOF analysis

Biochemistry. 2003 Oct 14;42(40):11798-807. doi: 10.1021/bi034611q.

Abstract

Cytosolic phospholipase A(2)gamma (cPLA(2)gamma) is a calcium-independent, membrane-associated phospholipase A(2) that possesses a C-terminal prenylation motif (-CCLA) whose covalent structure cannot be deduced from the primary sequence alone. Accordingly, we overexpressed human cPLA(2)gamma containing an N-terminal His tag ((His)(6)cPLA(2)gamma) in Sf9 cells and quantitatively solubilized and purified the enzyme by sequential immobilized metal affinity and Mono Q column chromatographies. The final preparation appeared as a single 61 kDa band after SDS-PAGE/silver-staining, possessed high lysophospholipase activity (50 micromol min(-1) mg(-1)), and was inhibited by, but did not hydrolyze, palmitoyl-CoA. Radiolabeling of recombinant human cPLA(2)gamma with [(3)H]-mevalonolactone in the absence of statins and subsequent cleavage of prenyl groups with Raney nickel revealed that the enzyme is only farnesylated and is not geranylgeranylated. Analysis of CNBr-digested cPLA(2)gamma by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight (MALDI/TOF-TOF) mass spectrometry demonstrated the presence of a farnesyl moiety at Cys-538, cleavage of the Cys(538)-Cys(539) bond, and carboxymethylation of the resultant C-terminal prenylated cysteine. Collectively, these results describe the solubilization and purification of recombinant cPLA(2)gamma to homogeneity and identify cPLA(2)gamma as a farnesylated protein that undergoes at least three sequential posttranslational modifications that likely facilitate its targeting and interactions with its membrane substrates.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Motifs / genetics
  • Amino Acid Sequence
  • Animals
  • Cloning, Molecular
  • Cytosol / enzymology
  • Endopeptidases / metabolism*
  • Enzyme Activation / drug effects
  • Enzyme Inhibitors / pharmacology
  • Group IV Phospholipases A2
  • Humans
  • Hydrolysis
  • Lysophospholipase / antagonists & inhibitors
  • Lysophospholipase / metabolism
  • Methylation
  • Molecular Sequence Data
  • Palmitoyl Coenzyme A / pharmacology
  • Peptide Fragments / genetics
  • Peptide Fragments / isolation & purification*
  • Peptide Fragments / metabolism*
  • Phospholipases A / biosynthesis
  • Phospholipases A / genetics
  • Phospholipases A / isolation & purification*
  • Phospholipases A / metabolism*
  • Protein Prenylation
  • Recombinant Proteins / genetics
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • Solubility
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / methods
  • Spodoptera / enzymology
  • Spodoptera / genetics

Substances

  • Enzyme Inhibitors
  • Peptide Fragments
  • Recombinant Proteins
  • Palmitoyl Coenzyme A
  • Phospholipases A
  • Group IV Phospholipases A2
  • Lysophospholipase
  • Endopeptidases