The ClpP serine peptidase is a tetradecameric degradation molecular machine involved in many physiological processes. It becomes a competent ATP‐dependent protease when coupled with Clp‐ATPases. Small chemical compounds, acyldepsipeptides (ADEPs), are known to cause the dysregulation and activation of ClpP without ATPases and have potential as novel antibiotics. Previously, structural studies of ClpP from various species revealed its structural details, conformational changes, and activation mechanism. Although product release through side exit pores has been proposed, the detailed driving force for product release remains elusive. Herein, we report crystal structures of ClpP from Bacillus subtilis (BsClpP) in unforeseen ADEP‐bound states. Cryo‐electron microscopy structures of BsClpP revealed various conformational states under different pH conditions. To understand the conformational change required for product release, we investigated the relationship between substrate hydrolysis and the pH‐lowering process. The production of hydrolyzed peptides from acidic and basic substrates by proteinase K and BsClpP lowered the pH values. Our data, together with those of previous findings, provide insight into the molecular mechanism of product release by the ClpP self‐compartmentalizing protease.

Structural insights into ClpP protease side exit pore‐opening by a pH drop coupled with substrate hydrolysis

The vast majority of genomic sequences are automatically annotated using various software programs. The accuracy of these annotations depends heavily on the very few manual annotation efforts that combine verified experimental data with genomic sequences from model organisms. Here, we summarize the updated functional annotation of Bacillus subtilis strain 168, a quarter century after its genome sequence was first made public. Since the last such effort 5 years ago, 1168 genetic functions have been updated, allowing the construction of a new metabolic model of this organism of environmental and industrial interest. The emphasis in this review is on new metabolic insights, the role of metals in metabolism and macromolecule biosynthesis, functions involved in biofilm formation, features controlling cell growth, and finally, protein agents that allow class discrimination, thus allowing maintenance management, and accuracy of all cell processes. New ‘genomic objects’ and an extensive updated literature review have been included for the sequence, now available at the International Nucleotide Sequence Database Collaboration (INSDC: AccNum AL009126.4).

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/1751-7915.14257

A model industrial workhorse: Bacillus subtilis strain 168 and its genome after a quarter of a century

http://www.cell.com/article/S221112472300712X/pdf

ECPAS/Ecm29-mediated 26S proteasome disassembly is an adaptive response to glucose starvation

The 26S proteasome consists of loosely associated 20S catalytic and 19S regulatory complexes. Although approximately half of the proteasomes in eukaryotic cells exist as free 20S complexes, our mechanistic and physiological understanding of 26S dissociation remains incomplete. Here, we show that glucose starvation in mammalian cells results in the uncoupling of 26S holoenzymes into intact 20S and 19S complexes. Subcomplex affinity-purification and quantitative mass spectrometry revealed that Ecm29 proteasome adaptor and scaffold (ECPAS) is a crucial mediator of this structural remodeling. The loss of ECPAS abrogated 26S dissociation, leading to decreased degradation of 20S proteasome substrates, such as puromycylated polypeptides and lysine-less cyclin B. In silico modeling analysis suggested that the conformational changes of ECPAS may commence the disassembly process. ECPAS was also essential for proper endoplasmic reticulum stress response and cell survival during glucose starvation. In addition, we evaluated the role of ECPAS in vivo using the mouse xenograft model and observed that glucose-deprived tumor tissues had significantly elevated 20S proteasome levels. Collectively, our results indicate that the 20S-19S disassembly mediated by ECPAS is a novel mechanism adapting global proteolysis to physiological needs and an effective cellular strategy against proteotoxic stress.

ECPAS/Ecm29-Mediated 26S Proteasome Disassembly Is an Adaptive Response to Glucose Starvation

https://www.molcells.org/journal/download_pdf.php?doi=10.14348/molcells.2023.2197

Quo Vadis Experimental Structural Biology?

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 domains of CCT3/4, thereby displacing PFD from TRiC. ATP-induced TRiC closure rearranges the contacts of PhLP2A domains within the closed chamber. In the presence of substrate, actin and PhLP2A segregate into opposing chambers, each binding to the positively charged inner surfaces formed by CCT1/3/6/8. Notably, actin induces a conformational change in PhLP2A, causing its N-terminal helices to extend across the inter-ring interface to directly contact a hydrophobic groove in actin. Our findings reveal an ATP-driven PhLP2A structural rearrangement cycle within the TRiC chamber to facilitate folding. Highlights - Structural analysis of TRiC-mediated folding cycle with cochaperones PhLP2A and PFD. - The interactions of PhLP2A and PFD with TRiC are mutually exclusive. - PhLP2A domains interact in a subunit-specific manner with the TRiC chamber. - PhLP2A domains are rearranged in ATP-closed TRiC to contact actin across the ring interface

/pdf/a-structural-vista-of-phosducin-like-phlp2a-chaperonin-tric-v61x41zo.pdf

Hyunmin Kim

Papers

Structural insights into ClpP protease side exit pore‐opening by a pH drop coupled with substrate hydrolysis

A structural vista of phosducin-like PhLP2A-chaperonin TRiC cooperation during the ATP-driven folding cycle