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

John Hamilton Beattie, Alison Wood, Gary James Duncan

    Research output: Contribution to journalArticle

    24 Citations (Scopus)

    Abstract

    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
    JournalElectrophoresis
    Volume20
    Issue number7
    Publication statusPublished - Jun 1999

    Keywords

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

    Cite this

    Beattie, J. H., Wood, A., & Duncan, G. J. (1999). Rat metallothionein-2 contains N-alpha-acetylated and unacetylated isoforms. Electrophoresis, 20(7), 1613-1618.

    Rat metallothionein-2 contains N-alpha-acetylated and unacetylated isoforms. / Beattie, John Hamilton; Wood, Alison; Duncan, Gary James.

    In: Electrophoresis, Vol. 20, No. 7, 06.1999, p. 1613-1618.

    Research output: Contribution to journalArticle

    Beattie, JH, Wood, A & Duncan, GJ 1999, 'Rat metallothionein-2 contains N-alpha-acetylated and unacetylated isoforms', Electrophoresis, vol. 20, no. 7, pp. 1613-1618.
    Beattie JH, Wood A, Duncan GJ. Rat metallothionein-2 contains N-alpha-acetylated and unacetylated isoforms. Electrophoresis. 1999 Jun;20(7):1613-1618.
    Beattie, John Hamilton ; Wood, Alison ; Duncan, Gary James. / Rat metallothionein-2 contains N-alpha-acetylated and unacetylated isoforms. In: Electrophoresis. 1999 ; Vol. 20, No. 7. pp. 1613-1618.
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    abstract = "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.",
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    N2 - 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.

    AB - 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.

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    KW - translation

    KW - capillary electrophoresis

    KW - mass spectrometry

    KW - electrokinetic capillary chromatography

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    KW - separation

    KW - cells

    KW - isometallothioneins

    KW - electrophoresis

    KW - induction

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