Protein folding in the cell: Challenges and progress

Department of Biochemistry & Molecular Biology, University of Massachusetts, Amherst, MA 01003, USA.
Current Opinion in Structural Biology (Impact Factor: 7.2). 02/2011; 21(1):32-41. DOI: 10.1016/
Source: PubMed


It is hard to imagine a more extreme contrast than that between the dilute solutions used for in vitro studies of protein folding and the crowded, compartmentalized, sticky, spatially inhomogeneous interior of a cell. This review highlights recent research exploring protein folding in the cell with a focus on issues that are generally not relevant to in vitro studies of protein folding, such as macromolecular crowding, hindered diffusion, cotranslational folding, molecular chaperones, and evolutionary pressures. The technical obstacles that must be overcome to characterize protein folding in the cell are driving methodological advances, and we draw attention to several examples, such as fluorescence imaging of folding in cells and genetic screens for in-cell stability.

Download full-text


Available from: Lila M Gierasch, Jan 29, 2014
32 Reads
  • Source
    • "In recent years, considerable effort has been devoted to the optimization of bacterial expression systems for antibody production (Gershenson and Gierasch 2011). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Recombinant antibodies are used with great success in many different diagnostic and therapeutic applications. A variety of protein expression systems are available, but nowadays almost all therapeutic antibodies are produced in mammalian cell lines due to their complex structure and glycosylation requirements. However, production of clinical-grade antibodies in mammalian cells is very expensive and time-consuming. On the other hand, Escherichia coli (E. coli) is known to be the simplest, fastest and most cost-effective recombinant expression system, which usually achieves higher protein yields than mammalian cells. Indeed, it is one of the most popular host in the industry for the expression of recombinant proteins. In this work, a trivalent single-chain fragment variable (scFv)-based N-terminal trimerbody, specific for native laminin-111, was expressed in human embryonic kidney 293 cells and in E. coli. Mammalian and bacterially produced anti-laminin trimerbody molecules display comparable functional and structural properties, although importantly the yield of trimerbody expressed in E. coli was considerably higher than in human cells. These results demonstrated that E. coli is a versatile and efficient expression system for multivalent trimerbody-based molecules that is suitable for their industrial production.
    AMB Express 12/2015; 5(1):137. DOI:10.1186/s13568-015-0137-0
  • Source
    • "Both crowding and confinement are expected to increase the stability of folded proteins with respect to the corresponding unfolded species, on the assumption that volume exclusion ought to favor more compact conformations . Although recent evaluations seemed to suggest that the effects of crowding on protein stability are modest [13] [14], it must be emphasized that it has been always difficult to compare the effects of crowding and confinement, mainly because most studies have been performed on different proteins. The availability of a friendly system like Yfh1 prompted us to make a detailed comparison [15]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Protein stability is an important issue for the interpretation of a wide variety of biological problems but its assessment is at times difficult. The most common parameter employed to describe protein stability is the temperature of melting, at which the populations of folded and unfolded species are identical. This parameter may yield ambiguous results. It would always be preferable to measure the whole stability curve. The calculation of this curve is greatly facilitated whenever it is possible to observe cold denaturation. Using Yfh1, one of the few proteins whose cold denaturation occurs at neutral pH and low ionic strength, we could measure the variation of its full stability curve under several environmental conditions. Here we show the advantages of gauging stability as a function of external variables using stability curves. Copyright © 2015. Published by Elsevier B.V.
    Biophysical chemistry 05/2015; DOI:10.1016/j.bpc.2015.05.007 · 1.99 Impact Factor
  • Source
    • "Large amounts of SSPs are produced in the ER of rice endosperm and, thus, the ER in rice endosperm is densely packed with polypeptides. In such a crowded cellular environment, unfolded proteins are often produced through stochastic errors during protein synthesis or by perturbation due to adverse environmental changes (Gershenson and Gierasch, 2011; Hartl et al., 2011). The accumulated unfolded proteins may form aggregations, resulting in perturbed cellular homeostasis when these unfolded proteins bind to other proteins. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Large amounts of seed storage proteins (SSPs) are produced in the maturing endosperm of rice seeds. Rice SSPs are synthesized as secretory proteins on the rough endoplasmic reticulum (ER), and are transported and deposited into protein complexes called protein bodies (PB-I and PB-II). Due to the high production of SSPs, unfolded SSPs may be generated during this process. However, it was previously unclear how such unfolded proteins are selected among synthesized products and removed from the ER to maintain protein quality in the endosperm. Since Hrd3/SEL1L recognizes unfolded proteins in yeast and mammalian protein quality control systems, the role of OsHrd3 in protein quality control in rice endosperm was investigated. Co-immunoprecipitation experiments demonstrated that OsHrd3 interacts with components of the Hrd1 ubiquitin ligase complex such as OsOS-9 and OsHrd1 in rice protoplasts. Endosperm-specific suppression of OsHrd3 in transgenic rice reduced the levels of polyubiquitinated proteins and resulted in unfolded protein responses (UPRs) in the endosperm, suggesting that OsHrd3-mediated polyubiquitination plays an important role in ER quality control. It was found that a cysteine-rich 13kDa prolamin, RM1, was polyubiquitinated in wild-type (WT) seeds but not in OsHrd3 knockdown (KD) seeds. RM1 formed aberrant aggregates that were deposited abnormally in OsHrd3 KD seeds, resulting in deformed PB-I. Therefore, the quality of protein bodies is maintained by polyubiquitination of unfolded SSPs through the Hrd1 ubiquitin ligase system in rice endosperm. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.
    Journal of Experimental Botany 05/2015; 66(15). DOI:10.1093/jxb/erv229 · 5.53 Impact Factor
Show more