title: High-resolution structure of Bombyx mori lipoprotein 7: crystallographic determination of the identity of the protein and its potential role in detoxification.
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 interactions 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.
authors.affiliation: Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland.
authors.forename: Agnieszka J
authors.initials: AJ
authors.lastname: Pietrzyk
authors.forename: Santosh
authors.initials: S
authors.lastname: Panjikar
authors.forename: Anna
authors.initials: A
authors.lastname: Bujacz
authors.forename: Jochen
authors.initials: J
authors.lastname: Mueller-Dieckmann
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Lochynska
authors.forename: Mariusz
authors.initials: M
authors.lastname: Jaskolski
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Bujacz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D012831:Bombyx / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D008074:Lipoproteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D008074:Lipoproteins