Characterization of an α-macroglobulin-like glycoprotein isolated from the plasma of the soft tick Ornithodoros moubata

Petr Kopáček, Christoph Weise, Saravanan Thangamani, Kateřina Vítová, Libor Grubhoffer

Research output: Contribution to journalArticle

40 Citations (Scopus)

Abstract

We report the identification of the first representative of the α-2- macroglobulin family identified in terrestrial invertebrates. An abundant acidic glycoprotein was isolated from the plasma of the soft tick Ornithodoros moubata. Its molecular mass is about 420 kDa in the native state, whereas in SDS/PAGE it migrates as one band of 190 kDa under nonreducing conditions and a band of 92 kDa when reduced. Chemical deglycosylation reveals that it is composed of two different subunits, designated A and B. The N-terminal amino-acid sequence of subunit A is similar to the N-terminus of invertebrate α-2-macroglobulin. Sequence analysis of several internal peptides confirms that the tick protein belongs to the α-2-macroglobulin family, and the protein is therefore referred to as tick α-macroglobulin (TAM). Functional analyses strengthen this assignment. TAM inhibits trypsin and thermolysin cleavage of the high-molecular-weight substrate azocoll in a manner similar to that of bovine α-2-macroglobulin. This effect is abolished by pretreatment of TAM with methylamine. In the presence of TAM, trypsin is protected against active-site inhibition by soybean trypsin inhibitor. We cloned and sequenced a PCR product containing sequences from both subunits and spanning the N-terminus of subunit B and the putative 'bait region' (a segment of α-2-macroglobulin which serves as target for various proteases). This indicates that the two subunits are generated from a precursor polypeptide by posttranslational processing.

Original languageEnglish (US)
Pages (from-to)465-475
Number of pages11
JournalEuropean Journal of Biochemistry
Volume267
Issue number2
DOIs
StatePublished - 2000
Externally publishedYes

Fingerprint

Argasidae
Ornithodoros
Macroglobulins
Glycoproteins
Plasmas
Ticks
Invertebrates
Trypsin
Arthropod Proteins
Thermolysin
Peptides
Trypsin Inhibitors
Molecular mass
Soybeans
Sequence Analysis
Polyacrylamide Gel Electrophoresis
Amino Acid Sequence
Catalytic Domain
Peptide Hydrolases
Molecular Weight

Keywords

  • α-macroglobulin
  • Invertebrate immunity
  • Ornithodoros moubata
  • Tick plasma

ASJC Scopus subject areas

  • Biochemistry

Cite this

Characterization of an α-macroglobulin-like glycoprotein isolated from the plasma of the soft tick Ornithodoros moubata. / Kopáček, Petr; Weise, Christoph; Thangamani, Saravanan; Vítová, Kateřina; Grubhoffer, Libor.

In: European Journal of Biochemistry, Vol. 267, No. 2, 2000, p. 465-475.

Research output: Contribution to journalArticle

Kopáček, Petr ; Weise, Christoph ; Thangamani, Saravanan ; Vítová, Kateřina ; Grubhoffer, Libor. / Characterization of an α-macroglobulin-like glycoprotein isolated from the plasma of the soft tick Ornithodoros moubata. In: European Journal of Biochemistry. 2000 ; Vol. 267, No. 2. pp. 465-475.
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AB - We report the identification of the first representative of the α-2- macroglobulin family identified in terrestrial invertebrates. An abundant acidic glycoprotein was isolated from the plasma of the soft tick Ornithodoros moubata. Its molecular mass is about 420 kDa in the native state, whereas in SDS/PAGE it migrates as one band of 190 kDa under nonreducing conditions and a band of 92 kDa when reduced. Chemical deglycosylation reveals that it is composed of two different subunits, designated A and B. The N-terminal amino-acid sequence of subunit A is similar to the N-terminus of invertebrate α-2-macroglobulin. Sequence analysis of several internal peptides confirms that the tick protein belongs to the α-2-macroglobulin family, and the protein is therefore referred to as tick α-macroglobulin (TAM). Functional analyses strengthen this assignment. TAM inhibits trypsin and thermolysin cleavage of the high-molecular-weight substrate azocoll in a manner similar to that of bovine α-2-macroglobulin. This effect is abolished by pretreatment of TAM with methylamine. In the presence of TAM, trypsin is protected against active-site inhibition by soybean trypsin inhibitor. We cloned and sequenced a PCR product containing sequences from both subunits and spanning the N-terminus of subunit B and the putative 'bait region' (a segment of α-2-macroglobulin which serves as target for various proteases). This indicates that the two subunits are generated from a precursor polypeptide by posttranslational processing.

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