tailieunhanh - Báo cáo khoa học: Amino acids Thr56 and Thr58 are not essential for elongation factor 2 function in yeast

Yeast elongation factor 2 is an essential protein that contains two highly conserved threonine residues, T56 and T58, that could potentially be phos-phorylated by the Rck2 kinase in response to environmental stress. The importance of residues T56 and T58 for elongation factor 2 function in yeast was studied using site directed mutagenesis and functional comple-mentation. | ỊFEBS Journal Amino acids Thr56 and Thr58 are not essential for elongation factor 2 function in yeast Galyna Bartish1 2 Hossein Moradi1 2 and Odd Nygard1 1 Schoolof Life Sciences Sodertorns hogskola Huddinge Sweden 2 Department of Cell Biology Arrhenius Laboratories Stockholm University Sweden Keywords elongation factor 2 functional complementation osmostress phosphorylation yeast Correspondence O. Nygard Schoolof Life Sciences Sodertorns hogskola S-141 89 Huddinge Sweden Fax 46 8608 4510 Tel 46 8608 4701 E-mail Received 10 January 2007 revised 27 June 2007 accepted 17 August 2007 doi Yeast elongation factor 2 is an essential protein that contains two highly conserved threonine residues T56 and T58 that could potentially be phosphorylated by the Rck2 kinase in response to environmental stress. The importance of residues T56 and T58 for elongation factor 2 function in yeast was studied using site directed mutagenesis and functional complementation. Mutations T56D T56G T56K T56N and T56V resulted in nonfunctional elongation factor 2 whereas mutated factor carrying point mutations T56M T56C T56S T58S and T58V was functional. Expression of mutants T56C T56S and T58S was associated with reduced growth rate. The double mutants T56M T58W and T56M T58V were also functional but the latter mutant caused increased cell death and considerably reduced growth rate. The results suggest that the physiological role of T56 and T58 as phosphorylation targets is of little importance in yeast under standard growth conditions. Yeast cells expressing mutants T56C and T56S were less able to cope with environmental stress induced by increased growth temperatures. Similarly cells expressing mutants T56M and T56M T58W were less capable of adapting to increased osmolarity whereas cells expressing mutant T58V behaved normally. All mutants tested were retained their ability to bind to ribosomes in vivo. However mutants T56D T56G and T56K were .