Molecular features of the UNC-45 chaperone critical for binding and folding muscle myosin

  title={Molecular features of the UNC-45 chaperone critical for binding and folding muscle myosin},
  author={D. Hellerschmied and Anita Lehner and Nina Frani{\vc}evi{\'c} and Renato Arnese and Chloe A Johnson and Antonia Vogel and A. Meinhart and R. Kurzbauer and L. Deszcz and L. Gazda and M. Geeves and T. Clausen},
  journal={Nature Communications},
Myosin is a motor protein that is essential for a variety of processes ranging from intracellular transport to muscle contraction. Folding and assembly of myosin relies on a specific chaperone, UNC-45. To address its substrate-targeting mechanism, we reconstitute the interplay between Caenorhabditis elegans UNC-45 and muscle myosin MHC-B in insect cells. In addition to providing a cellular chaperone assay, the established system enabled us to produce large amounts of functional muscle myosin… Expand
Mutations in conserved residues of the myosin chaperone UNC-45 result in both reduced stability and chaperoning activity
The biophysical assays performed on purified proteins show that all of the mutations result in reduced myosin chaperone activity but not overall protein stability, suggesting that these mutations only cause protein instability in the in vivo setting and that these conserved regions may be involved in UNC-45 protein stability/ regulation via post translational modifications, protein-protein interactions, or some other unknown mechanism. Expand
Mutational analysis of the structure and function of the chaperone domain of UNC-45B
  • I. Gaziova, T. Moncrief, +6 authors A. F. Oberhauser
  • Biology, Chemistry
  • 2020
A novel approach that combines biophysical and biological tools to study UNC-45B/myosin interactions in mechanistic detail is developed and may provide critical insights into the molecular nature of the pathogenesis of many muscle disorders stemming from mutations in sarcomeric proteins. Expand
Mutational Analysis of the Structure and Function of the Chaperoning Domain of UNC-45B.
The in-vivo data show that the R805W mutation appeared to have the most drastic detrimental effect on the structure and organization of the worm sarcomeres, indicating a crucial role of R805 in UCS-client interactions. Expand
Pathogenic Variants in the Myosin Chaperone UNC-45B Cause Progressive Myopathy with Eccentric Cores.
It is demonstrated that UNC-45B impairment manifests as a chaperonopathy with progressive muscle pathology, which discovers the previously unknown conserved role of UNC- 45B in myofibrillar organization. Expand
X-ray crystallographic and molecular dynamic analyses of Drosophila melanogaster embryonic muscle myosin define domains responsible for isoform-specific properties.
All atom molecular dynamics simulations on EMB in its nucleotide-free state and a derivative homology model containing 61 amino acid substitutions unique to the indirect flight muscle isoform (IFI) suggest that differences in the identity of residues within the relay and the converter that are encoded for by MHC alternative exons 9 and 11 directly contribute to increased mobility of these regions in IFI relative to EMB. Expand
The ATPase mechanism of myosin 15, the molecular motor mutated in DFNB3 human deafness
The kinetic analysis shows the MYO15 motor domain has a moderate duty ratio and weak thermodynamic coupling between ADP and actin binding, consistent with MyO15 being adapted for strain sensing as a monomer, or processive motility if oligomerized into ensembles. Expand
The ATPase mechanism of myosin 15, the molecular motor mutated in DFNB3 human deafness
A kinetic characterization of the ATPase motor domain enables future studies into how deafness-causing mutations affect MYO15 and disrupt stereocilia trafficking necessary for hearing and is consistent with MyO15 being kinetically adapted for processive motility when oligomerized. Expand
Molecular cloning and expression dynamics of UNC-45B upon heat shock in the muscle of yellowtail
The results show that the increase in UNC- 45B expression levels can reflect heat shock response sensitively, and it is suggested that UNC-45B can repair the denatured myosin during heat shock exposure in yellowtail. Expand
Artificial Intelligence Set to Reverse Engineer Drug Targeting in the Cell.
  • Ariel Fernández
  • Computer Science, Medicine
  • ACS pharmacology & translational science
  • 2021
This work has shown that drug-induced protein folding in vivo is off limits to computational modeling efforts, but this situation may change as artificial intelligence empowers molecular dynamics and enables the deconstruction of in vivo cooperativity for structural adaptation. Expand


The Myosin Chaperone UNC-45 Is Organized in Tandem Modules to Support Myofilament Formation in C. elegans
In vivo analyses reveal the elongated canyon of the UCS domain as a myosin-binding site and show that multimeric UNC-45 chains support organization of sarcomeric repeats. Expand
Tracking UNC-45 chaperone-myosin interaction with a titin mechanical reporter.
A novel approach is devised, to the knowledge, to analyze the interaction of UNC-45 with the myosin motor domain at the single molecule level using atomic force microscopy, and it is shown that after mechanical unfolding, the motor domain interfered with refolding of the otherwise robust I27 modules, presumably by recruiting them into a misfolded state. Expand
Unc45 Activates Hsp90-dependent Folding of the Myosin Motor Domain*
This analysis of vertebrate Unc45 isoforms clearly demonstrates a direct role for Unc45 in Hsp90-mediated myosin motor domain folding and highlights major differences between the isoforms in substrate specificity and mechanism. Expand
Role of the Myosin Assembly Protein UNC-45 as a Molecular Chaperone for Myosin
UNC-45 functions both as a molecular chaperone and as an Hsp90 co-chaperone for myosin, which can explain previous findings of altered assembly and decreased accumulation of myOSin in UNC-45 mutants of Caenorhabditis elegans. Expand
The myosin co-chaperone UNC-45 is required for skeletal and cardiac muscle function in zebrafish.
A role for unc45b in zebrafish motility consistent with a function in myosin thick filament assembly and stability is confirmed and novel roles for this gene in the function and morphogenesis of the developing heart and jaw are uncovered. Expand
Drosophila UNC-45 prevents heat-induced aggregation of skeletal muscle myosin and facilitates refolding of citrate synthase.
In conclusion, this in vitro study provides insight into the fate of muscle myosin under stress conditions and suggests that UNC-45 protects and maintains the contractile machinery during in vivo stress. Expand
Chaperone-mediated folding and assembly of myosin in striated muscle
It is concluded that multimeric complexes of nascent myosin filaments associated with Hsc70 and Hsp90 are intermediates in the folding and assembly pathway of muscle myos in post-mitotic C2C12 myocytes. Expand
Myosin II Folding Is Mediated by a Molecular Chaperonin*
It is concluded that the molecular assembly of myosin is mediated by the eukaryotic cytosolic chaperonin with folding of the motor domain as the slow step in the pathway. Expand
Unc45b Forms a Cytosolic Complex with Hsp90 and Targets the Unfolded Myosin Motor Domain
M mammalian Unc45b is a cytosolic protein that forms a stable complex with Hsp90, selectively binds the unfolded conformation of the myosin motor domain, and promotes motor domain folding. Expand
The UNC-45 myosin chaperone: from worms to flies to vertebrates.
In this chapter, biochemical, structural, and genetic analyses of UNC-45 are presented in Caenorhabditis elegans, Drosophila melanogaster, and various vertebrates to provide insights into UNC- 45 functions, its potential mechanism of action, and its roles in human disease. Expand