Title
HRI, a stress response eIF2α kinase, exhibits structural and functional stability at high temperature and alkaline conditions
Author
Varsha Bhavnani, Kaviraj Swarnendu, Laxman Savergave, Arjun Singh Raghuwanshi, Ankit Kumar, Avinash Kumar, Jayanta Pal
Year
2016
Journal
International Journal of Biological Macromolecules
Abstract
The Heme Regulated Inhibitor (HRI) is a key regulator of protein synthesis in mammalian cells. Once activated under heme-deficiency and other stress conditions, it phosphorylates the α subunit of eukaryotic initiation factor 2 (eIF2α) leading to inhibition of protein synthesis. In the present study, our objective was to establish the structural and functional credentials of this kinase so as to qualify it as a stress responsive eIF2α kinase. When the protein was subjected to high temperature, 45 °C (above mammalian heat shock temperature), it could still phosphorylate the substrate, indicating its potential as a stress response kinase. At a temperature beyond 45 °C, loss in secondary structure of the kinase is attributable to loss of its function. Furthermore, no significant structural changes were observed at the broad pH range of 3.0–10.0. The Kinase incubated at any pH between 8.0–10.0, exhibited more than 60% of its kinase activity, demonstrating structural and functional stability of the kinase at an alkaline pH. These data taken together establish that the structural stability of this kinase at high temperature and alkaline conditions is due to conservation of its secondary structure and that the resulting functional activity qualifies this kinase as a stress responsive kinase.
Instrument
J-815
Keywords
Circular dichroism, Secondary structure, Thermal stability, Thermodynamics, Chemical stability, Biochemistry