title: Gene structure and M20T polymorphism of the Schistosoma mansoni Sm14 fatty acid-binding protein. Molecular, functioanl, and immunoprotection analysis.
abstract: The Schistosoma mansoni Sm14 antigen belongs to the fatty acid-binding protein family and is considered a vaccine candidate against at least two parasite worms, Fasciola hepatica and S. mansoni. Here the genomic sequence and the polymorphism of Sm14 have been characterized for the first time. We found that the conserved methionine at position 20 is polymorphic, being exchangeable with threonine (M20T). To evaluate the function of the amino acid residue at this position, we have also constructed the mutant Sm14-A20 besides the two native isoforms (Sm14-M20 and Sm14-T20). The three purified recombinant His(6)-tagged Sm14 proteins (rSm14-M20, rSm14-T20, and rSm14-A20) present a predominant beta-barrel structure as shown by CD spectroscopy. Thermal and urea unfolding studies evidenced a higher structural stability of rSm14-M20 over the other forms (rSm14-M20>rSm14-T20>rSm14-A20). All of the Sm14 proteins were able to bind 11-(dansylamino)undecanoic acid (DAUDA) without substantial difference in the binding affinity. However, rSm14-M20 exhibited a higher affinity for natural fatty acids than the rSm14-T20 and rSm14-A20 proteins as judged by competitive experiments against DAUDA (rSm14-M20>rSm14-T20>rSm14-A20). The rSm14-M20 or rSm14-T20 isoforms but not the rSm14-A20 mutant was able to induce significant protection against S. mansoni cercariae challenge in immunized mice. The level of protection efficacy correlates with the extent of structure stability of the recombinant Sm14 isoforms and mutant.
authors.affiliation: Instituto Butantan, Avenida Vital Brasil 1500, 05503-900, São Paulo, Brazil.
authors.forename: Celso Raul Romero
authors.initials: CR
authors.lastname: Ramos
authors.forename: Rita Cassia Rossi
authors.initials: RC
authors.lastname: Figueredo
authors.forename: Thelma Aguiar
authors.initials: TA
authors.lastname: Pertinhez
authors.forename: Mônica Magno
authors.initials: MM
authors.lastname: Vilar
authors.forename: Ana Lúcia Tabet Oller
authors.initials: AL
authors.lastname: do Nascimento
authors.forename: Miriam
authors.initials: M
authors.lastname: Tendler
authors.forename: Isaías
authors.initials: I
authors.lastname: Raw
authors.forename: Alberto
authors.initials: A
authors.lastname: Spisni
authors.forename: Paulo Lee
authors.initials: PL
authors.lastname: Ho
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D001938:Brazil; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002942:Circular Dichroism; D017931:DNA Primers; D050612:Fatty Acid Transport Proteins; D050556:Fatty Acid-Binding Proteins; D005260:Female; D005843:Geography; D015801:Helminth Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D007438:Introns; D008297:Male; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D005810:Multigene Family; D020125:Mutation, Missense; D009363:Neoplasm Proteins; D011110:Polymorphism, Genetic; D012550:Schistosoma mansoni / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013816:Thermodynamics
chemical_list: D002352:Carrier Proteins; D017931:DNA Primers; D050612:Fatty Acid Transport Proteins; D050556:Fatty Acid-Binding Proteins; D015801:Helminth Proteins; D026901:Membrane Transport Proteins; D009363:Neoplasm Proteins; C068709:SM14 protein, Schistosoma mansoni