Heat shock modulates phosphorylation status and activity of nucleoside diphosphate kinase in cultured sugarcane cells |
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Authors: | Sunethra Dharmasiri H Michael Harrington Nihal Dharmasiri |
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Institution: | (1) Department of Biology, Texas State University, 601, University Drive, San Marcos, USA;(2) Western Association of Agriculture Experiment Station Directors, Colorado State University, 16 Administration Building, Fort Collins, CO 80523, USA |
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Abstract: | Nucleoside diphosphate kinase (NDPK) is involved in the regeneration of nucleoside triphosphates (NTPs) through its phosphotransferase
activity via an autophosphorylating histidine residue. Additionally, autophosphorylation of serine and/or threonine residues
is documented for NDPKs from various organisms. However, the metabolic significance of serine/threonine phosphorylation has
not been well characterized. In this study we report the cloning and characterization of NDPKI from cultured sugarcane (Saccharum officinarum L. line H50-7209) cells, and modulation of serine autophosphorylation of NDPK1 in response to heat-shock (HS). Heat-shock
treatment at 40°C for 2 h resulted in a 40% reduction in labeled phosphoserine in NDPK1. This dephosphorylation was accompanied
by an increase in NDPK enzyme activity. In contrast, NDPK1 in cultured tobacco (cv. W-38) cells did not show changes in autophosphorylation
or increased enzyme activity in response to HS. The mRNA or protein level of NDPK1 did not increase in response to HS. Sugarcane
cells sustain the constitutive protein synthesis in addition to heat-shock protein synthesis during HS, while constitutive
protein synthesis is significantly reduced in tobacco cells during HS. Thus, HS modulation of NDPK1 activity and serine dephosphorylation
in sugarcane cells may represent an important physiological role in maintaining cellular metabolic functions during heat stress. |
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