The DNLZ/HEP zinc-binding subdomain is critical for regulation of the mitochondrial chaperone HSPA9.

Human mitochondrial DNLZ/HEP regulates the catalytic activity and solubility of the mitochondrial hsp70 chaperone Here, we investigate the role that the DNLZ zinc-binding and C-terminal subdomains play in regulating Hduanyu18429. We show that truncations lacking portions of the zinc-binding subdomain (ZBS) do not affect the solubility of or its ATPase domain, whereas those containing the ZBS and at least 10 residues following this subdomain enhance chaperone solubility. Binding measurements further show that DNLZ requires its ZBS to form a stable complex with the Hduanyu18429 ATPase domain, and ATP hydrolysis measurements reveal that the ZBS is critical for full stimulation of Hduanyu18429 catalytic activity. We also examined if DNLZ is active in vivo. We found that DNLZ partially complements the growth of Δzim17 Saccharomyces cerevisiae, and we discovered that a Zim17 truncation lacking a majority of the C-terminal subdomain strongly complements growth like full-length Zim17. These findings provide direct evidence that human DNLZ is a functional ortholog of Zim17. In addition, they implicate the pair of antiparallel β-strands that coordinate zinc in Zim17/DNLZ-type proteins as critical for binding and regulating hsp70 chaperones.

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