Soung‐Hun Roh

Single-particle electron cryo-microscopy (cryo-EM) is an emerging tool for resolving structures of conformationally heterogeneous particles; however, each structure is derived from an average of many particles with presumed identical conformations. We used a 3.5-Å cryo-EM reconstruction with imposed D7 symmetry to further analyze structural heterogeneity among chemically identical subunits in each GroEL oligomer. Focused classification of the 14 subunits in each oligomer revealed three dominant

The folding of newly synthesized proteins and the maintenance of pre-existing proteins are essential in sustaining a living cell. A network of molecular chaperones tightly guides the folding, intracellular localization, and proteolytic turnover of proteins. Many of the key regulators of cell growth and differentiation have been identified as clients of molecular chaperones, which implies that chaperones are potential mediators of oncogenesis. In this review, we briefly provide an overview of the

Rotary vacuolar adenosine triphosphatases (V-ATPases) drive transmembrane proton transport through a V_o proton channel subcomplex. Despite recent high-resolution structures of several rotary ATPases, the dynamic mechanism of proton pumping remains elusive. Here, we determined a 2.7-Å cryo-electron microscopy (cryo-EM) structure of yeast V_o proton channel in nanodisc that reveals the location of ordered water molecules along the proton path, details of specific protein-lipid

AML1-ETO is the most common fusion oncoprotein causing acute myeloid leukemia (AML), a disease with a 5-year survival rate of only 24%. AML1-ETO functions as a rogue transcription factor, altering the expression of genes critical for myeloid cell development and differentiation. Currently, there are no specific therapies for AML1-ETO-positive AML. While known for decades to be the translational product of a chimeric gene created by the stable chromosome translocation t(8;21)(q22;q22), it is not

The adulteration of dietary supplements with drugs is potentially dangerous for human health. In this study, a method was used to test simultaneously for the presence of three synthetic PDE-5 inhibitors (sildenafil, vardenafil and tadalafil), and sibutramine and its two major metabolites (N-desmethylsibutramine and N-didesmethylsibutramine) using ultra-performance liquid chromatography (UPLC) coupled with quadrupole-time-of-flight mass spectrometry (Q-TOF MS) in dietary supplements. This approac

The GroEL/GroES chaperonin system assists the folding of many proteins, through conformational transitions driven by ATP hydrolysis. Although structural information about bullet-shaped GroEL:ES₁ complexes has been extensively reported, the substrate interactions of another functional complex, the football-shaped GroEL:ES₂, remain elusive. Here, we report single-particle cryo-EM structures of reconstituted wild-type GroEL:ES₂ complexes with a chemically denatured

Nanodiscs, consisting of a lipid bilayer surrounded by membrane scaffold proteins (MSPs), are extensively used to study membrane proteins (MPs) because they provide a stable lipid environment. However, the precise mechanism governing MP behavior within the nanodisc remains elusive. Here, we examined the cryo-EM structures of various MPs reconstituted in nanodiscs from EMPIAR. By analyzing the heterogeneity and interactions in the nanodiscs, we discovered that MPs display a distinct spatial prefe

Accurate folding of proteins in living cells often requires the cooperative support of molecular chaperones. Eukaryotic group II chaperonin Tailless complex polypeptide 1-Ring Complex (TRiC) accomplishes this task by providing a folding chamber for the substrate that is regulated by an Adenosine triphosphate (ATP) hydrolysis-dependent cycle. Once delivered to and recognized by TRiC, the nascent substrate enters the folding chamber and undergoes folding and release in a stepwise manner. During th

Proper cellular proteostasis, essential for viability, requires a network of chaperones and cochaperones. ATP-dependent chaperonin TRiC/CCT partners with cochaperones prefoldin (PFD) and phosducin-like proteins (PhLPs) to facilitate the folding of essential eukaryotic proteins. Using cryoEM and biochemical analyses, we determine the ATP-driven cycle of TRiC-PFD-PhLP2A interaction. In the open TRiC state, PhLP2A binds to the chamber's equator while its N-terminal H3-domain binds to the apical dom

Cryogenic-electron microscopy (cryo-EM) is the preferred method to determine 3D structures of proteins and to study diverse material systems that intrinsically have radiation or air sensitivity. Current cryo-EM sample preparation methods provide limited control over the sample quality, which limits the efficiency and high throughput of 3D structure analysis. This is partly because it is difficult to control the thickness of the vitreous ice that embeds specimens, in the range of nanoscale, depen

SUMMARY The ATP-dependent ring-shaped chaperonin TRiC/CCT is essential for cellular proteostasis. To uncover why some eukaryotic proteins can only fold with TRiC assistance, we reconstituted the folding of β-tubulin using human Prefoldin and TRiC. We find unstructured β-tubulin is delivered by Prefoldin to the open TRiC chamber followed by ATP-dependent chamber closure. CryoEM resolves four near-atomic resolution structures containing progressively folded β-tubulin intermediates within the close