Drosophila UNC-45 prevents heat-induced aggregation of skeletal muscle myosin and facilitates refolding of citrate synthase.
UNC-45 belongs to the UCS (UNC-45, CRO1, She4p) domain protein family, whose members interact with various classes of myosin. Here we provide structural and biochemical evidence that Escherichia coli-expressed Drosophila UNC-45 (DUNC-45) maintains the integrity of several substrates during heat-induced stress in vitro. DUNC-45 displays chaperone function in suppressing aggregation of the muscle myosin heavy meromyosin fragment, the myosin S-1 motor domain, alpha-lactalbumin and citrate synthase. Biochemical evidence is supported by electron microscopy, which reveals the first structural evidence that DUNC-45 prevents inter- or intra-molecular aggregates of skeletal muscle heavy meromyosin caused by elevated temperatures. We also demonstrate for the first time that UNC-45 is able to refold a denatured substrate, urea-unfolded citrate synthase. Overall, 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.
Melkani
Girish C
GC
Department of Biology and the Molecular Biology Institute, San Diego State University, San Diego, CA 92182-4614, USA.
Lee
Chi F
CF
Cammarato
Anthony
A
Bernstein
Sanford I
SI
D000818:Animals; D002950:Citrate (si)-Synthase / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D018869:Heat-Shock Response; D007768:Lactalbumin / Q000378:metabolism; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D009119:Muscle Contraction; D015879:Myosin Subfragments / Q000378:metabolism*; D017510:Protein Folding; D024744:Skeletal Muscle Myosins / Q000378:metabolism*
D029721:Drosophila Proteins; D018832:Molecular Chaperones; D015879:Myosin Subfragments; C550552:UNC-45 protein, Drosophila; D007768:Lactalbumin; D002950:Citrate (si)-Synthase; D024744:Skeletal Muscle Myosins
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