title: Tri-domain bifunctional inhibitor of metallocarboxypeptidases A and serine proteases isolated from marine annelid Sabellastarte magnifica.
abstract: This study describes a novel bifunctional metallocarboxypeptidase and serine protease inhibitor (SmCI) isolated from the tentacle crown of the annelid Sabellastarte magnifica. SmCI is a 165-residue glycoprotein with a molecular mass of 19.69 kDa (mass spectrometry) and 18 cysteine residues forming nine disulfide bonds. Its cDNA was cloned and sequenced by RT-PCR and nested PCR using degenerated oligonucleotides. Employing this information along with data derived from automatic Edman degradation of peptide fragments, the SmCI sequence was fully characterized, indicating the presence of three bovine pancreatic trypsin inhibitor/Kunitz domains and its high homology with other Kunitz serine protease inhibitors. Enzyme kinetics and structural analyses revealed SmCI to be an inhibitor of human and bovine pancreatic metallocarboxypeptidases of the A-type (but not B-type), with nanomolar K(i) values. SmCI is also capable of inhibiting bovine pancreatic trypsin, chymotrypsin, and porcine pancreatic elastase in varying measures. When the inhibitor and its nonglycosylated form (SmCI N23A mutant) were overproduced recombinantly in a Pichia pastoris system, they displayed the dual inhibitory properties of the natural form. Similarly, two bi-domain forms of the inhibitor (recombinant rSmCI D1-D2 and rSmCI D2-D3) as well as its C-terminal domain (rSmCI-D3) were also overproduced. Of these fragments, only the rSmCI D1-D2 bi-domain retained inhibition of metallocarboxypeptidase A but only partially, indicating that the whole tri-domain structure is required for such capability in full. SmCI is the first proteinaceous inhibitor of metallocarboxypeptidases able to act as well on another mechanistic class of proteases (serine-type) and is the first of this kind identified in nature.
authors.affiliation: Centro de Estudio de Proteínas, Facultad de Biología, Universidad de la Habana, 10400 La Habana, Cuba.
authors.forename: Maday
authors.initials: M
authors.lastname: Alonso-del-Rivero
authors.forename: Sebastian A
authors.initials: SA
authors.lastname: Trejo
authors.forename: Mey L
authors.initials: ML
authors.lastname: Reytor
authors.forename: Monica
authors.initials: M
authors.lastname: Rodriguez-de-la-Vega
authors.forename: Julieta
authors.initials: J
authors.lastname: Delfin
authors.forename: Joaquin
authors.initials: J
authors.lastname: Diaz
authors.forename: Yamile
authors.initials: Y
authors.lastname: González-González
authors.forename: Francesc
authors.initials: F
authors.lastname: Canals
authors.forename: Maria Angeles
authors.initials: MA
authors.lastname: Chavez
authors.forename: Francesc X
authors.initials: FX
authors.lastname: Aviles
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D007611:Aprotinin / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D055162:Biocatalysis / Q000187:drug effects; D002268:Carboxypeptidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002417:Cattle; D003001:Cloning, Molecular; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011077:Polychaeta / Q000235:genetics*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D017422:Sequence Analysis, DNA; D057057:Serine Proteases / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000737:chemistry / Q000235:genetics* / Q000494:pharmacology
chemical_list: D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; D007611:Aprotinin; D002268:Carboxypeptidases; D057057:Serine Proteases