Rat metallothionein-2 contains N-alpha-acetylated and unacetylated isoforms

John Hamilton Beattie, Alison Wood, Gary James Duncan

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)


Mammalian metallothioneins (MT), are characteristically N-alpha-acetylated and the presence of an unblocked N-terminus has not previously been reported. On-line capillary electrophoresis-electrospray mass spectrometry of hepatic MT-2 from rats injected with zinc revealed two isoforms differing by a mass equivalent to that of a single acetyl group. The lower mass component constituted > 20% of total MT-2 protein and both MT-2 isoforms were separated by reversed-phase high-performance liquid chromatography. The identity of each fraction was confirmed by matrix-assisted laser desorption ionisation mass spectrometry, and amino acid analysis and N-terminal sequencing revealed that the lower mass isoform was unblocked at the N-terminus and had an amino acid composition and sequence which is characteristic of rat MT-2. Thus the complementary techniques of mass spectrometry and K-terminal sequencing demonstrated conclusively that purified MT-2 from zinc-treated rats contains an unacetylated isoform. We propose that the cotranslational acetylation of rat MT-2 may under some circumstances be inefficient compared to that in other nonrodent species, where we have detected only trace levels of unacetylated MT isoforms.

Original languageEnglish
Pages (from-to)1613-1618
Number of pages6
Issue number7
Publication statusPublished - Jun 1999


  • Metallothionein
  • isoforms
  • acetylation
  • translation
  • capillary electrophoresis
  • mass spectrometry
  • electrokinetic capillary chromatography
  • liver
  • separation
  • cells
  • isometallothioneins
  • electrophoresis
  • induction


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