Journal Article

Identification of Amino Acid Substitutions that Render the <i>Arabidopsis</i> Cytokinin Receptor Histidine Kinase AHK4 Constitutively Active

Kumiko Miwa, Kuniko Ishikawa, Kazunori Terada, Hisami Yamada, Tomomi Suzuki, Takafumi Yamashino and Takeshi Mizuno

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 48, issue 12, pages 1809-1814
Published in print December 2007 | ISSN: 0032-0781
Published online December 2007 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcm145
Identification of Amino Acid Substitutions that Render the Arabidopsis Cytokinin Receptor Histidine Kinase AHK4 Constitutively Active

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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In Arabidopsis, three genes (AHK2, AHK3 and AHK4/CRE1) encode histidine kinases (His-kinases), which serve as cytokinin receptors. To understand how the external cytokinin signal activates the His-kinase across the cell membrane, we exploited the power of microbial genetics to isolate several AHK4 mutants that function independently of cytokinin in both prokaryotic and eukaryotic assay systems. In each mutant, a single amino acid substitution within the second membrane-spanning segment, or within the region around the phosphorylation His site, renders the His-kinase constitutively active. These mutant receptors appear to have a ‘locked-on’ conformation, even in the absence of stimulus. We discuss the implications of these data for the structure and function of the cytokinin receptor His-kinases in plants.

Keywords: Cytokinin assay system with microbial cells; Cytokinin receptor; His–Asp phosphorelay signaling; His-kinase; Structure and function

Journal Article.  3405 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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