title: Crystallographic studies evidencing the high energy tolerance to disrupting the interface disulfide bond of thioredoxin 1 from white leg shrimp Litopenaeus vannamei.
abstract: Thioredoxin (Trx) is a small 12-kDa redox protein that catalyzes the reduction of disulfide bonds in proteins from different biological systems. A recent study of the crystal structure of white leg shrimp thioredoxin 1 from Litopenaeus vannamei (LvTrx) revealed a dimeric form of the protein mediated by a covalent link through a disulfide bond between Cys73 from each monomer. In the present study, X-ray-induced damage in the catalytic and the interface disulfide bond of LvTrx was studied at atomic resolution at different transmission energies of 8% and 27%, 12.8 keV at 100 K in the beamline I-24 at Diamond Light Source. We found that at an absorbed dose of 32 MGy, the X-ray induces the cleavage of the disulfide bond of each catalytic site; however, the interface disulfide bond was cleaved at an X-ray adsorbed dose of 85 MGy; despite being the most solvent-exposed disulfide bond in LvTrx (~50 Å2). This result clearly established that the interface disulfide bond is very stable and, therefore, less susceptible to being reduced by X-rays. In fact, these studies open the possibility of the existence in solution of a dimeric LvTrx.
authors.affiliation: Departamento de Medicina molecular y Bioprocesos, Instituto de Biotecnología (IBT), Universidad Nacional Autónoma de México (UNAM), Avenida Universidad 2001, Colonia Chamilpa, Cuernavaca 62210, Mexico.
authors.forename: Adam A
authors.initials: AA
authors.lastname: Campos-Acevedo
authors.affiliation: Departamento de Medicina molecular y Bioprocesos, Instituto de Biotecnología (IBT), Universidad Nacional Autónoma de México (UNAM), Avenida Universidad 2001, Colonia Chamilpa, Cuernavaca 62210, Mexico. rudino@ibt.unam.mx.
authors.forename: Enrique
authors.initials: E
authors.lastname: Rudiño-Piñera
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D060829:Arthropod Proteins / Q000737:chemistry*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D003553:Cystine / Q000737:chemistry*; D004795:Enzyme Stability; D008958:Models, Molecular; D008969:Molecular Sequence Data; D033561:Penaeidae / Q000201:enzymology; D017433:Protein Structure, Secondary; D013879:Thioredoxins / Q000737:chemistry*
chemical_list: D060829:Arthropod Proteins; D003553:Cystine; D013879:Thioredoxins