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Structure of alpha-2-macroglobulin from the arthropod limulus-polyphemus

Academic Article
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Overview

authors

  • Armstrong, P. B.
  • Mangel, W. F.
  • Wall, J. S.
  • Hainfield, J. F.
  • Vanholde, K. E.
  • Ikai, A.
  • Quigley, James

publication date

  • 1991

journal

  • Journal of Biological Chemistry  Journal

abstract

  • A structural and functional homologue of vertebrate alpha 2-macroglobulin (alpha 2M) has been identified in the hemolymph and blood cells of the arthropod Limulus polyphemus, one of the oldest living fossil invertebrates (Quigley, J. P., and Armstrong, P. B. (1985) J. Biol. Chem. 260, 12715-12719). The subunit molecular mass is 185 kDa. The native molecular mass, determined by scanning transmission electron microscopy (STEM) under conditions in which the linear relationship between the STEM large angle detector signal and specimen mass thickness allows the determination of the total macromolecular mass, was 354 +/- 35 kDa. Sedimentation equilibrium measurements gave a value of 366 kDa, independent of solute concentration. Sedimentation velocity experiments indicated a homogeneous component with a frictional ratio of 1.41. Thus, the native structure appears to be a dimer, with a somewhat extended conformation. The behavior during gel permeation chromatography was anomalous, yielding an apparent molecular mass approximately half-way between that expected for the dimeric and tetrameric configurations. Transmission electron microscopy of negatively stained preparations revealed a dimeric butterfly-like structure that collapsed following reaction with chymotrypsin.

subject areas

  • Animals
  • Centrifugation, Density Gradient
  • Chromatography, Gel
  • Chymotrypsin
  • Electrophoresis, Polyacrylamide Gel
  • Horseshoe Crabs
  • Microscopy, Electron, Scanning
  • Molecular Weight
  • Protein Conformation
  • alpha-Macroglobulins
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Identity

International Standard Serial Number (ISSN)

  • 0021-9258

PubMed ID

  • 1703530
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Additional Document Info

start page

  • 2526

end page

  • 2530

volume

  • 266

issue

  • 4

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