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Role of the loop L-4,L-5 in allosteric regulation in mtHsp70s: in vivo significance of domain communication and its implications in protein translocation

Samaddar, Madhuja and Goswami, Arvind Vittal and Purushotham, Jaya and Hegde, Pushpa and D'Silva, Patrick (2014) Role of the loop L-4,L-5 in allosteric regulation in mtHsp70s: in vivo significance of domain communication and its implications in protein translocation. In: MOLECULAR BIOLOGY OF THE CELL, 25 (14). pp. 2129-2142.

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Official URL: http://dx.doi.org/ 10.1091/mbc.E14-03-0821


Mitochondrial Hsp70 (mtHsp70) is essential for a vast repertoire of functions, including protein import, and requires effective interdomain communication for efficient partner-protein interactions. However, the in vivo functional significance of allosteric regulation in eukaryotes is poorly defined. Using integrated biochemical and yeast genetic approaches, we provide compelling evidence that a conserved substrate-binding domain (SBD) loop, L-4,L-5, plays a critical role in allosteric communication governing mtHsp70 chaperone functions across species. In yeast, a temperature-sensitive L-4,L-5 mutation (E467A) disrupts bidirectional domain communication, leading to compromised protein import and mitochondrial function. Loop L-4,L-5 functions synergistically with the linker in modulating the allosteric interface and conformational transitions between SBD and the nucleotide-binding domain (NBD), thus regulating interdomain communication. Second-site intragenic suppressors of E467A isolated within the SBD suppress domain communication defects by conformationally altering the allosteric interface, thereby restoring import and growth phenotypes. Strikingly, the suppressor mutations highlight that restoration of communication from NBD to SBD alone is the minimum essential requirement for effective in vivo function when primed at higher basal ATPase activity, mimicking the J-protein-bound state. Together these findings provide the first mechanistic insights into critical regions within the SBD of mtHsp70s regulating interdomain communication, thus highlighting its importance in protein translocation and mitochondrial biogenesis.

Item Type: Journal Article
Additional Information: Copy right for this article belongs to the AMER SOC CELL BIOLOGY, 8120 WOODMONT AVE, STE 750, BETHESDA, MD 20814-2755 USA
Department/Centre: Division of Biological Sciences > Biochemistry
Date Deposited: 03 Sep 2014 08:54
Last Modified: 03 Sep 2014 08:54
URI: http://eprints.iisc.ac.in/id/eprint/49725

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