title: The oxidoreductase behavior of protein disulfide isomerase impedes fold maturation of endoplasmic reticulum-processed proteins in the pivotal structure-coupled step of oxidative folding: implications for subcellular protein trafficking.
abstract: Protein disulfide isomerase (PDI), the chief endoplasmic reticulum (ER) resident oxidoreductase chaperone, is known to catalyze the maturation of disulfide bond-containing proteins primarily through oxidation and isomerization functions. The rate-determining step in the oxidative regeneration path of disulfide bond-containing proteins generally couples chemical thiol-disulfide-exchange reactions to a physical conformational folding reaction. We have determined the impact of PDI and its subdomains on the rate-determining step in ribonuclease A folding and on the physical structure-forming step of select ER-processed proteins including RNase A. This was facilitated through application of a novel chemical tool to exclusively populate native disulfide-containing intermediates in unstructured forms. The described biochemical inroad permits a deconvoluted study of the physical half-process in the rate-determining step from its chemical counterpart. Analysis of folding kinetics of RNase A and other proteins reveals that the highly evolved oxidoreductase activity of PDI masks its chaperone-like activity, impedes conformational folding of ER-processed proteins, and limits its potential to accelerate the rate-determining step in oxidative regeneration. Implications of the heretofore unknown and anomalous self-limiting behavior of PDI are discussed in the context of oxidative maturation and misfolding in vivo.
authors.affiliation: Department of Chemistry, University of Texas at El Paso, El Paso, Texas 79968, USA.
authors.forename: Veronica
authors.initials: V
authors.lastname: Gonzalez
authors.forename: Rituraj
authors.initials: R
authors.lastname: Pal
authors.forename: Mahesh
authors.initials: M
authors.lastname: Narayan
mesh_terms: D004721:Endoplasmic Reticulum / Q000201:enzymology*; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism*; D019704:Protein Disulfide-Isomerases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012259:Ribonuclease, Pancreatic / Q000737:chemistry / Q000378:metabolism*
chemical_list: D018832:Molecular Chaperones; D012259:Ribonuclease, Pancreatic; D019704:Protein Disulfide-Isomerases