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Structural similarity between lung surfactant protein D and conglutinin. Two distinct, C-type lectins containing collagen-like sequences

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  • J Lu
  • ,
  • H Wiedemann
  • ,
  • U Holmskov
  • ,
  • S Thiel
  • R Timpl
  • ,
  • K B Reid
  • Department of Medical Microbiology and Immunology
Preparations of bovine lung surfactant D (SP-D) and conglutinin were examined by electron microscopy, gel-filtration and SDS/PAGE. SP-D is composed of non-covalently linked subunits, of 160 kDa, which each contain three, disulphide-linked, 44-kDa polypeptide chains. In the electron microscope a single 160-kDa subunit of SP-D appears as a 45.8 +/- 3-nm-long rod connected to a small globular 'head'. Particles were also seen which correspond to non-covalently linked dimers, trimers and tetramers of the 160-kDa monomer subunit of SP-D. The tetramer structure contains 12 polypeptide chains and is very similar to the electron microscopy images and model reported by Strang et al. [Strang, C. J., Slayter, US., Lachmann, P. J. and Davis, A. E. (1986) Biochem. J. 236, 3811-389] for bovine conglutinin in which four 160-kDa subunits are disulphide-linked to give a molecule of expected molecular mass of 528 kDa. This study confirmed the findings by Strang et al. in the above paper for intact conglutinin and also emphasised that the rod-like structures, of length 37.6 +/- 3.7 nm, seen in the conglutinin subunits were significantly shorter than those in SP-D despite the close similarity in amino acid sequence (79% identify) and chain length between the two proteins. In addition, a truncated form of conglutinin was found in the conglutinin preparations, due to limited proteolysis of the Arg-Ala bond at position 54 in the 44-kDa chains. These truncated conglutinin chains yield a subunit composed of three shortened, non-disulphide-linked, chains and this subunit appears as a monomer with a rod length of 34.2 +/- 2.8 nm in the electron microscope. On gel-filtration, a proportion of the SP-D preparation behaved, as expected, as a molecule with an apparent molecular mass of 600 kDa. The remainder of the SP-D preparation behaved as aggregated material with a molecular mass greater than 900 kDa which yielded no distinct structures in the electron microscope. Intact conglutinin was eluted at a position greater than 900 kDa but yet provided clear electron microscopy images of the tetramer structure described above.(ABSTRACT TRUNCATED AT 400 WORDS)
Original languageEnglish
JournalEuropean Journal of Biochemistry
Pages (from-to)793-9
Number of pages7
Publication statusPublished - 1 Aug 1993

    Research areas

  • Amino Acid Sequence, Animals, Cattle, Chromatography, Gel, Collagen, Collectins, Electrophoresis, Polyacrylamide Gel, Glycoproteins, Humans, Lectins, Microscopy, Electron, Molecular Sequence Data, Protein Conformation, Pulmonary Surfactant-Associated Protein D, Pulmonary Surfactants, Serum Globulins

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