Serine/threonine kinase activity in the putative histidine kinase-like ethylene receptor NTHK1 from tobacco.
A histidine kinase-based signaling system has been proposed to function in ethylene signal transduction pathway of plants and one ethylene receptor has been found to possess His kinase activity. Here we demonstrate that a His kinase-like ethylene receptor homologue NTHK1 from tobacco has serine/threonine (Ser/Thr) kinase activity, but no His kinase activity. Evidence obtained by analyzing acid/base stability, phosphoamino acid and substrate specificity of the phosphorylated kinase domain, supports this conclusion. In addition, mutation of the presumptive phosphorylation site His (H378) to Gln did not affect the kinase activity whereas deletion of the ATP-binding domain eliminated it, indicating that the conserved His (H378) is not required for the kinase activity and this activity is intrinsic to the NTHK1-KD. Moreover, confocal analysis of NTHK1 expression in insect cells and plant cells suggested the plasma membrane localization of the NTHK1 protein. Thus, NTHK1 may represent a distinct Ser/Thr kinase-type ethylene receptor and function in an alternative mechanism for ethylene signal transduction.
Xie
Can
C
Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, Peoples Republic of China.
Zhang
Jin-Song
JS
Zhou
Hua-Lin
HL
Li
Jian
J
Zhang
Zhi-Gang
ZG
Wang
Dao-Wen
DW
Chen
Shou-Yi
SY
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D000071677:Histidine Kinase; D009154:Mutation; D010766:Phosphorylation; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013379:Substrate Specificity; D014026:Nicotiana / Q000201:enzymology* / Q000235:genetics
D010940:Plant Proteins; D011956:Receptors, Cell Surface; C083750:ethylene receptors, plant; D000255:Adenosine Triphosphate; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D000071677:Histidine Kinase