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Hsp70 chaperones assist in a large variety of protein-folding processes in the cell. Crucial for these activities is the regulation of Hsp70 by Hsp40 cochaperones. DnaJ, the bacterial homologue of Hsp40, stimulates ATP hydrolysis by DnaK (Hsp70) and thus mediates capture of substrate protein, but is also known to possess chaperone activity of its own. The first structure of a complete functional dimeric DnaJ was determined and the mobility of its individual domains in solution was investigated. Crystal structures of the complete molecular cochaperone DnaJ from Thermus thermophilus comprising the J, GF and C-terminal domains and of the J and GF domains alone showed an ordered GF domain interacting with the J domain. Structure-based EPR spin-labelling studies as well as cross-linking results showed the existence of multiple states of DnaJ in solution with different arrangements of the various domains, which has implications for the function of DnaJ.
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http://dx.doi.org/10.1107/S0907444913010640 | DOI Listing |
Future Oncol
July 2025
Department of Medical Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
The DNAJ/HSP40 family consists of three distinct subfamilies (DNAJA, DNAJB, and DNAJC) and is the largest and most diverse co-chaperone proteins for HSP70. The DNAJA subfamily, comprising four members, assumes a pivotal role in various pathological conditions such as cystic fibrosis, neurodegenerative disorders, and cancer. This review comprehensively investigates the participation and underlying mechanisms of DNAJA proteins in tumor proliferation and metastasis, with a specific focus on their influence on the accumulation of mutant p53 proteins.
View Article and Find Full Text PDFDNA Repair (Amst)
May 2025
School of Basic Medical Sciences, Capital Medical University, Beijing, China; Institute for Cancer Research, Chinese Institutes for Medical Research, Beijing, China.
The DnaJ heat shock protein family (HSP40) is the biggest chaperone family in mammalian cells, mainly functioning as cochaperone of HSP70 to maintain proteostasis and cellular homeostasis under both normal and stressful conditions. Although the functions of HSP70s have been extensively studied in diverse biological pathways and senesces including genome maintenance, HSP40s' biological functions at basal state or in response to exogenous insults remain largely under-investigated. Emerging evidence shows that HSP40 proteins participate in genome maintenance pathways and modulate cancer therapy efficacy.
View Article and Find Full Text PDFBiochim Biophys Acta Proteins Proteom
July 2025
Systems Toxicology Group, FEST Division, CSIR- Indian Institute of Toxicology Research, Vishvigyan Bhawan, 31, Mahatma Gandhi Marg, Lucknow 226001, Uttar Pradesh, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201 002, India. Electronic address:
DNAJ proteins, also known as HSP40s, are co-chaperones that regulate the multifunctionality of HSP70s in maintaining cellular protein homeostasis. The heterogeneous family of DNAJ co-chaperones is classified into three classes (A, B and C), where structural diversity within the class defines their specific functions. Among three classes, the DNAJB class of co-chaperones are associated with cellular compartment-specific protein folding, disaggregation and degradation of proteins and enables effective targeting of a broad spectrum of aggregation-prone substrate proteins.
View Article and Find Full Text PDFCells
March 2025
Department of Biochemistry and Molecular Biology, School of Medicine, Kyung Hee University, Seoul 02447, Republic of Korea.
Hsp70, a 70 kDa molecular chaperone, plays a crucial role in maintaining protein homeostasis. It interacts with the DnaJ family of co-chaperones to modulate the functions of client proteins involved in various cellular processes, including transmembrane transport, extracellular vesicle trafficking, complex formation, and proteasomal degradation. Its presence in multiple cellular organelles enables it to mediate stress responses, apoptosis, and inflammation, highlighting its significance in disease progression.
View Article and Find Full Text PDFmBio
May 2025
Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, Connecticut, USA.
Molecular chaperones are critical for protein homeostasis. In bacteria, chaperone trigger factor (TF) folds proteins co-translationally, and chaperone DnaK requires a J-domain cochaperone and nucleotide exchange factor GrpE to fold proteins largely post-translationally. However, when the pathogen serovar Typhimurium faces the infection-relevant condition of cytoplasmic Mg starvation, DnaK reduces protein synthesis independently.
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