Ornithine decarboxylase encoded by chlorella virus PBCV-1

Tiara A. Morehead, James R. Gurnon, Byron Adams, Kenneth W. Nickerson, Lisa A. Fitzgerald, James L. Van Etten

Research output: Contribution to journalArticle

22 Scopus citations

Abstract

Sequence analysis of the 330-kb genome of chlorella virus PBCV-1 revealed an open reading frame, A207R, which encodes a protein with 37-41% amino acid identity to ornithine decarboxylase (ODC) from many eukaryotic organisms. The a207r gene was cloned and the protein was expressed as a His-A207R fusion protein in Escherichia coli. The recombinant protein catalyzes pyridoxal 5′-phosphate-dependent decarboxylation of ornithine to putrescine, the first step in the polyamine biosynthetic pathway. The enzyme has a pH optimum of 9.0 and a temperature optimum of 42°C, and it requires dithiothreitol for maximal activity. The enzyme has a Km for ornithine of 0.78 mM and a specific activity of 100 μmol/min/mg protein. PBCV-1 ODC is quite sensitive to the competitive inhibitor L-arginine and the irreversible inhibitor difluoromethylarginine but it is less sensitive to the irreversible inhibitor difluoromethylornithine. The a207r gene is expressed both early and late in PBCV-1 infection and is highly conserved among the chlorella viruses. The 42-kDa PBCV-1 ODC (372 amino acids) is the smallest ODC in the databases and, to our knowledge, is the first virus-encoded ODC.

Original languageEnglish (US)
Pages (from-to)165-175
Number of pages11
JournalVirology
Volume301
Issue number1
DOIs
StatePublished - 2002

Keywords

  • Chlorella viruses
  • Ornithine decarboxylase
  • Phycodnaviridae
  • Polyamines

ASJC Scopus subject areas

  • Virology

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