title: Crystal structure of the 30 K protein from the silkworm Bombyx mori reveals a new member of the β-trefoil superfamily.
abstract: The hemolymph of the fifth instar larvae of the silkworm Bombyx mori contains a group of homologous proteins with a molecular weight of approximately 30 kDa, termed B. mori low molecular weight lipoproteins (Bmlps), which account for about 5% of the total plasma proteins. These so-called "30 K proteins" have been reported to be involved in the innate immune response and transportation of lipid and/or sugar. To elucidate their molecular functions, we determined the crystal structure of a 30 K protein, Bmlp7, at 1.91Å. It has two distinct domains: an all-α N-terminal domain (NTD) and an all-β C-terminal domain (CTD) of the β-trefoil fold. Comparative structural analysis indicates that Bmlp7 represents a new family, adding to the 14 families currently identified, of the β-trefoil superfamily. Structural comparison and simulation suggest that the NTD has a putative lipid-binding cavity, whereas the CTD has a potential sugar-binding site. However, we were unable to detect the binding of either lipid or sugar. Therefore, further investigations are needed to characterize the molecular function of this protein.
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei Anhui 230027, People's Republic of China.
authors.forename: Jie-Pin
authors.initials: JP
authors.lastname: Yang
authors.forename: Xiao-Xiao
authors.initials: XX
authors.lastname: Ma
authors.forename: Yong-Xing
authors.initials: YX
authors.lastname: He
authors.forename: Wei-Fang
authors.initials: WF
authors.lastname: Li
authors.forename: Yan
authors.initials: Y
authors.lastname: Kang
authors.forename: Rui
authors.initials: R
authors.lastname: Bao
authors.forename: Yuxing
authors.initials: Y
authors.lastname: Chen
authors.forename: Cong-Zhao
authors.initials: CZ
authors.lastname: Zhou
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D012831:Bombyx / Q000737:chemistry*; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D006458:Hemolymph / Q000737:chemistry; D019476:Insect Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D019476:Insect Proteins