High-resolution structure of Bombyx mori lipoprotein 7: Crystallographic determination of the identity of the protein and its potential role in detoxification

Agnieszka J. Pietrzyk, Santosh Panjikar, Anna Bujacz, Jochen Mueller-Dieckmann, Malgorzata Lochynska, Mariusz Jaskolski, Grzegorz Bujacz

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Abstract

Three crystal structures of a lipoprotein (Bmlp7) of unknown function, a member of the 30 kDa lipoprotein family from mulberry silkworm (Bombyx mori L.) haemolymph, have been determined. The 1.33 Å resolution structure is an excellent example of how a precise crystallographic study can contribute to protein identification. The correct sequence of this haemolymph-isolated protein was assigned thanks to superb-quality electron-density maps. Two unexpected cadmium cations were found in this crystal structure [Bmlp7-I(Cd)] and their presence may be connected to a detoxification mechanism in this insect. For a comparison of the metal-binding sites, the crystal structure of a platinum complex (Bmlp7-Pt) was also solved at 1.94 Å resolution. The third (2.50 Å resolution) structure, of the native protein harvested in a different season (Bmlp7-II), corresponds to a different polymorph with an altered pattern of intermolecular inter-actions and with a total absence of cadmium ions and highlights the possible involvement of Bmlp7 in the response to environmental pollution. The N-terminal domain of Bmlp7 has a fold resembling a clockwise spiral created by six helices and can be classified as a VHS domain. The C-terminal domain is folded as a Β-trefoil. The biological function of Bmlp7 is unknown, but its structural homology to sugar-binding proteins suggests that, in analogy to other 30 kDa haemolymph lipoproteins, it could play a role as an anti-apoptotic factor or function in the immune response of the insect to fungal infections.

Original languageEnglish
Pages (from-to)1140-1151
Number of pages12
JournalActa Crystallographica Section D: Biological Crystallography
Volume68
Issue number9
DOIs
Publication statusPublished - Sep 2012
Externally publishedYes

Keywords

  • Β-trefoil
  • 30 kDa lipoprotein family
  • Bombyx mori
  • haemolymph
  • haemolymph proteins
  • protein sequencing
  • silkworm

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