Histidine kinase receptors

Maslennikov I, Klammt C, Hwang E, Kefala G, Okamura M, Esquivies L, Mors K, Glaubitz C, Kwiatkowski W, Jeon YH, Choe S (2010) Membrane domain stmctures of three classes of histidine kinase receptors by cell-free expression and rapid NMR analysis. Proc Natl Acad Sci... 

Fig. 225 Consensus effects of Spd and Spm on cytokinin metabolism and signaling cascade. Description is same as in legends to Fig. 22.1. AHK2 histidine kinase receptor 2, AHK3 histidine kinase receptor 3, AHK4 histidine kinase receptor 4, AHPs histidine-containing phosphotransfer protein, RRs response regulators, CK cytokinin, CKX cytokinin dehydrogenase, CRFs cytokinin response msp.) factors...

The bacterial chemoreceptor (Figs. 11-8 and 19-5) has a very small ligand-binding domain and a larger internal domain that activates a histidine kinase. Many growth-factor receptors, including the insulin receptor (Figs. 11-11,11-12), have internal domains with protein tyrosine kinase activity. 

In Arabidopsis genome, there are in total 16 different histidine kinases. Besides the above mentioned cytokinin receptors, they function also as the receptors of phytohormone ethylene and light stimuli - phytochromes [216]. 

Abbreviations a-BFAs anteiso-branched fatty acids AGP acyl carrier protein BHLH active soluble domain of SREBP CNS central nervous system DSD delta 5 desaturase D6D delta 6 desaturase ER endoplasmic reticulum Hik histidine kinase HUFA highly unsaturated fatty acid LXR liver X receptor MUFA monounsaturated fatty add NF-Y nuclear factor Y PLs phospholipids PP peroxisome proliferator PPAR PP-activated receptor PPRE PP response element PUFA polyunsaturated fatty acid PUFA-BP PUFA binding protein PUFA-RE PUFA response element RXR retinoid X receptor SCAP SREBP cleavage-activating protein SCD steraroyl CoA desaturase SFA saturated fatty acid SRE sterol response... 

About 25,498 genes encoding proteins from 11 different families have been found. More than 14,000 ESTs were established from cDNAs. Many of the genes represent new families, some of which may be peculiar to plants. However, many others are homologous to those of C. elegans and H. sapiens. For example, developmentally important homeotic genes, marked by a homeo sequence as in animal genes, are present as are thousands of cell surface receptors. However, only Ser / Thr and histidine kinases are present in Arabidopsis. No tyrosine kinases have been identified. 

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