title: Structural effects of protein aging: terminal marking by deamidation in human triosephosphate isomerase.
abstract: Deamidation, the loss of the ammonium group of asparagine and glutamine to form aspartic and glutamic acid, is one of the most commonly occurring post-translational modifications in proteins. Since deamidation rates are encoded in the protein structure, it has been proposed that they can serve as molecular clocks for the timing of biological processes such as protein turnover, development and aging. Despite the importance of this process, there is a lack of detailed structural information explaining the effects of deamidation on the structure of proteins. Here, we studied the effects of deamidation on human triosephosphate isomerase (HsTIM), an enzyme for which deamidation of N15 and N71 has been long recognized as the signal for terminal marking of the protein. Deamidation was mimicked by site directed mutagenesis; thus, three mutants of HsTIM (N15D, N71D and N15D/N71D) were characterized. The results show that the N71D mutant resembles, structurally and functionally, the wild type enzyme. In contrast, the N15D mutant displays all the detrimental effects related to deamidation. The N15D/N71D mutant shows only minor additional effects when compared with the N15D mutation, supporting that deamidation of N71 induces negligible effects. The crystal structures show that, in contrast to the N71D mutant, where minimal alterations are observed, the N15D mutation forms new interactions that perturb the structure of loop 1 and loop 3, both critical components of the catalytic site and the interface of HsTIM. Based on a phylogenetic analysis of TIM sequences, we propose the conservation of this mechanism for mammalian TIMs.
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, México, D.F., México.
authors.forename: Ignacio
authors.initials: I
authors.lastname: de la Mora-de la Mora
authors.affiliation: Departamento de Bioquímica Y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México, D.F., México.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Torres-Larios
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, México, D.F., México.
authors.forename: Sergio
authors.initials: S
authors.lastname: Enríquez-Flores
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, México, D.F., México.
authors.forename: Sara-Teresa
authors.initials: ST
authors.lastname: Méndez
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, México, D.F., México.
authors.forename: Adriana
authors.initials: A
authors.lastname: Castillo-Villanueva
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, México, D.F., México.
authors.forename: Saúl
authors.initials: S
authors.lastname: Gómez-Manzo
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, México, D.F., México.
authors.forename: Gabriel
authors.initials: G
authors.lastname: López-Velázquez
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, México, D.F., México.
authors.forename: Jaime
authors.initials: J
authors.lastname: Marcial-Quino
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, México, D.F., México.
authors.forename: Angélica
authors.initials: A
authors.lastname: Torres-Arroyo
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, México, D.F., México.
authors.forename: Itzhel
authors.initials: I
authors.lastname: García-Torres
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, México, D.F., México.
authors.forename: Horacio
authors.initials: H
authors.lastname: Reyes-Vivas
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, México, D.F., México.
authors.forename: Jesús
authors.initials: J
authors.lastname: Oria-Hernández
mesh_terms: D000577:Amides / Q000378:metabolism*; D006801:Humans; D016297:Mutagenesis, Site-Directed; D011499:Protein Processing, Post-Translational; D017433:Protein Structure, Secondary; D014305:Triose-Phosphate Isomerase / Q000235:genetics / Q000378:metabolism*
chemical_list: D000577:Amides; D014305:Triose-Phosphate Isomerase