title: Crystal structure of earthworm fibrinolytic enzyme component B: a novel, glycosylated two-chained trypsin.
abstract: The earthworm fibrinolytic enzyme (EFE), belonging to a group of serine proteases with strong fibrinolytic activity, has been used in a mixture as an oral drug for prevention and treatment of thrombosis in East Asia. The EFE component b (EFE-b) is one of seven EFE components from Eisenia fetida, and among them it has nearly the highest fibrinolytic activity. Here, we report its crystal structure at a resolution of 2.06A. The structural analysis shows that EFE-b should be classified as a trypsin from earthworm. However, it is distinct from other trypsins. It is a two-chained protease with an N-terminal, pyroglutamated light chain and an N-glycosylated heavy chain. Furthermore, the heavy chain contains a novel structural motif, an eight-membered ring resulting from a disulfide bridge between two neighboring cysteine residues, and a cis peptide bond exists between these two cysteine residues. The crystal structure of EFE-b provides the structural basis for its high level of stability and reveals its complicated post-translational modifications in earthworm. This structure is the first reported for a glycosylated two-chained trypsin, which may provide useful clues to explain the origin and evolution of the chymotrypsin family.
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, P. R. China.
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.forename: Chao
authors.initials: C
authors.lastname: Wang
authors.forename: Mei
authors.initials: M
authors.lastname: Li
authors.forename: Ji-Ping
authors.initials: JP
authors.lastname: Zhang
authors.forename: Lu-Lu
authors.initials: LL
authors.lastname: Gui
authors.forename: Xiao-Min
authors.initials: XM
authors.lastname: An
authors.forename: Wen-Rui
authors.initials: WR
authors.lastname: Chang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D018360:Crystallography, X-Ray; D010450:Endopeptidases / Q000737:chemistry* / Q000235:genetics; D004795:Enzyme Stability; D006031:Glycosylation; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009835:Oligochaeta / Q000201:enzymology*; D011498:Protein Precursors / Q000235:genetics; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D014357:Trypsin / Q000737:chemistry* / Q000235:genetics
chemical_list: D011498:Protein Precursors; D010450:Endopeptidases; D014357:Trypsin; D002118:Calcium