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Serine/threonine kinase activity in the putative histidine kinase‐like ethylene receptor NTHK1 from tobacco
Author(s) -
Xie Can,
Zhang JinSong,
Zhou HuaLin,
Li Jian,
Zhang ZhiGang,
Wang DaoWen,
Chen ShouYi
Publication year - 2003
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.2003.01631.x
Subject(s) - map kinase kinase kinase , cyclin dependent kinase 9 , map2k7 , mitogen activated protein kinase kinase , biochemistry , ask1 , c raf , biology , signal transduction , kinase , protein kinase a , cyclin dependent kinase 2 , microbiology and biotechnology , chemistry
Summary 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.