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

作者：Pietrzyk Agnieszka J; Panjikar Santosh; Bujacz Anna; Mueller Dieckmann Jochen; Lochynska Malgorzata; Jaskolski Mariusz; Bujacz Grzegorz^*

来源：Acta Crystallographica Section D-Biological Crystallography, 2012, 68(9): 1140-1151.

DOI：10.1107/S0907444912021555

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 angstrom 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 angstrom resolution. The third (2.50 angstrom 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 beta-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 antiapoptotic factor or function in the immune response of the insect to fungal infections.

• 出版日期2012-9