SNF-related serine/threonine-protein kinase is an enzyme that in humans is encoded by the SNRK gene. SNRK (sucrose non-fermentation 1-related kinase) is a new member of the AMPK (adenosine monophosphate-activated protein kinase) -related superfamily, which is activated during angiogenesis.
SNF1 protein kinase superfamily
The plant's SnRK (sucrose non-fermenting 1-related protein kinases) is homologous to yeast SNF1 (sucrose non-fermenting 1) and mammalian AMPK (AMP-activated protein kinases). The three together form the SNF1 protein kinase superfamily. SNF1 in yeast can respond to low glucose signals, control meiosis and regulate the level of phosphorylation of related metabolic enzymes in the absence of nutrition. In addition, in addition to responding to nutritional deficiencies, SNF1 also responds to other environmental stresses such as sodium stress, heat shock, alkaline pH, and oxidation stress. Mammalian AMPK can be activated by AMP in a high AMP/ATP state or by the upstream protein kinase AMPK (AMP-activated protein kinase). Activated AMPK enables mammalian cells to respond to different stresses. More and more studies have shown that the AMPK complex can respond to glucose signals and is directly related to the occurrence of obesity and type 2 diabetes. Based on sequence similarity and conservation of the enzyme's active domain. Plant protein shock families can be divided into three subfamilies: SnRK1, SnRK2, and SnRK3, which are widely involved in the sugar metabolism pathway and respond to various osmotic stresses such as drought and salt stress.
SnRK1 subfamily
The SnRK1 subfamily SnRK1 has direct structural and functional homology with yeast SNF1 and mammalian AMPK. According to the similarity of amino acid sequences, SnRK1 is divided into two groups: SnRK1a and SnRK1b. SnRK1a is expressed in all plants, while SnRK1b is only found in plants of monocotyledons, and the highest expression is in seeds. The earliest cloned SnRK1 cDNA sequence (cRKIN1) is from a rye endosperm cDNA library. The amino acid sequence is 48% similar to SNF1 and encodes a 57.7 kD protein.
SnRK2 subfamily
The SnRK2 subfamily is different from the SnRK1 family. SnRK2 and SnRK3 are plant-specific gene families with fewer members. The first member of SnRK2 was PKABA1 isolated from an ABA-treated wheat embryo cDNA library (Cheeseman, 1988). In addition to being induced by ABA, PKABA1 expression can also be induced by dehydration stress. Based on the analysis of the genetic distance of known members of SnRK2, SnRK2 can be divided into two groups of SnRK2a and SnRK2b (Halford and Hardie, 1998). The members of the two groups differed in their amino acid content in the C-terminal acid patch, SnRK2a was rich in Asp, and SnRK2b was rich in Glu.
SnRK2 activity and regulation
Reversible phosphorylation is an essential process for cells to regulate metabolism. In the signaling pathways involved in ABA, the activation of protein kinases plays a key role, especially SnRK2 plays an important role in plants in response to osmotic stress and ABA stress. The expression of SnRK2 activity is based on autophosphorylation. Tobacco ASK1 is a homologous gene of Arabidopsis SnRK2.4. ASK1 kinase purified from BY-2 cells can be protein phosphatase 2A; and alkaline phosphatase can cause rice SRK2 members SAPK1 and SAPK2 to be lost under salt stress live. In abi1-1 dominant mutant strain, OST1 kinase activity can be activated by ABA. Inhibition of OST kinase confirms that protein phosphatase 2C (PP2C) ABI1 negatively regulates OST1 upstream of the ABA signaling pathway.
SnRK3 subfamily
SnRK3 subfamily Like SnRK2, the SnRK3 gene family exists only in plants. Compared with the SnRK1 family, the SnRK3 family has a larger number of members, and its members are more diverse. Most researches on SnRK3 have focused on the role of plants in resisting stress. The expression of WPK4 in members of the wheat SnRK3 family is affected by sucrose, light intensity, temperature, and hormones. Arabidopsis SnRK3 family members PKS3, PKS18 and CIPK3 can regulate plant growth, stomatal opening and closing and seed germination through ABA. The most in-depth study in the SnRK3 family is Arabidopsis SOS2.
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