title: The conformational stability and biophysical properties of the eukaryotic thioredoxins of Pisum sativum are not family-conserved.
abstract: Thioredoxins (TRXs) are ubiquitous proteins involved in redox processes. About forty genes encode TRX or TRX-related proteins in plants, grouped in different families according to their subcellular localization. For instance, the h-type TRXs are located in cytoplasm or mitochondria, whereas f-type TRXs have a plastidial origin, although both types of proteins have an eukaryotic origin as opposed to other TRXs. Herein, we study the conformational and the biophysical features of TRXh1, TRXh2 and TRXf from Pisum sativum. The modelled structures of the three proteins show the well-known TRX fold. While sharing similar pH-denaturations features, the chemical and thermal stabilities are different, being PsTRXh1 (Pisum sativum thioredoxin h1) the most stable isoform; moreover, the three proteins follow a three-state denaturation model, during the chemical-denaturations. These differences in the thermal- and chemical-denaturations result from changes, in a broad sense, of the several ASAs (accessible surface areas) of the proteins. Thus, although a strong relationship can be found between the primary amino acid sequence and the structure among TRXs, that between the residue sequence and the conformational stability and biophysical properties is not. We discuss how these differences in the biophysical properties of TRXs determine their unique functions in pea, and we show how residues involved in the biophysical features described (pH-titrations, dimerizations and chemical-denaturations) belong to regions involved in interaction with other proteins. Our results suggest that the sequence demands of protein-protein function are relatively rigid, with different protein-binding pockets (some in common) for each of the three proteins, but the demands of structure and conformational stability per se (as long as there is a maintained core), are less so.
authors.affiliation: Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Elche, Alicante, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Aguado-Llera
authors.forename: Ana Isabel
authors.initials: AI
authors.lastname: Martínez-Gómez
authors.forename: Jesús
authors.initials: J
authors.lastname: Prieto
authors.forename: Marco
authors.initials: M
authors.lastname: Marenchino
authors.forename: José Angel
authors.initials: JA
authors.lastname: Traverso
authors.forename: Javier
authors.initials: J
authors.lastname: Gómez
authors.forename: Ana
authors.initials: A
authors.lastname: Chueca
authors.forename: José L
authors.initials: JL
authors.lastname: Neira
mesh_terms: D000143:Acids / Q000494:pharmacology; D000595:Amino Acid Sequence; D055592:Biophysical Phenomena / Q000502:physiology*; D017124:Conserved Sequence / Q000502:physiology; D005057:Eukaryotic Cells / Q000378:metabolism; D057446:Hydrodynamics; D008969:Molecular Sequence Data; D005810:Multigene Family; D018532:Pisum sativum / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation / Q000187:drug effects; D011489:Protein Denaturation / Q000187:drug effects; D055503:Protein Multimerization; D055550:Protein Stability / Q000187:drug effects; D017386:Sequence Homology, Amino Acid; D013879:Thioredoxins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
chemical_list: D000143:Acids; D013879:Thioredoxins