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Protein Kinases

Protein Kinases. Primary elements in signal transduction - Phosphorylated residues by protein kinases: S, T, Y A Protein kinase can ⓟ hundreds of target proteins , thereby amplifying signals. - Activator of Protein Kinases: light, pathogen, growth regulators,

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Protein Kinases

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  1. Protein Kinases • Primary elements in signal transduction • - Phosphorylated residues by protein kinases: S, T, Y • A Protein kinase can ⓟ hundreds of target proteins, • thereby amplifying signals. • - Activator of Protein Kinases: • light, • pathogen, • growth regulators, • temperature change, • nutrition deprivation, • water stresses (drought, salt), etc

  2. The various classes of protein kinases found in plants. Ex) PKA, PKC GSK3, CKII

  3. Cell Surface Receptors May Have Catalytic Activity • Receptor Tyrosine Kinases • Receptor Tyrosine Phosphatases • Receptor Ser/Thr Kinases • Tyrosine linked receptors • Receptor guanylate cyclases • cell surface proteases

  4. Ligand Binding to Receptor Tyrosine Kinases Induces autophosphorylation Signaling Proteins That Bind to RTKs Are Activated by phosphorylation

  5. Receptor-Like Kinases (RLKs) • S-domain RLKs • 2. Leucine rich repeat (LRR) RLKs • 3. Epidermal growth factor (EGF)-like RLKs • 4. Lectin receptor kinases

  6. Plant Receptor-like Kinases Are Structurally Similar to Animal Receptor Tyrosine Kinases • S receptor kinase (SRK) • The first class is characterized by an extracellular S domain • The S domain was identified in S locus glycoproteins (SLGs) which regulate self-incompatibility in Brassica species.

  7. An example of S-domain RLK Fig. 18.59. General model for pollen tube incompatibility as a result of two way signaling between pollen tube and stigma.

  8. 2. Leucine-rich repeat (LRR) receptors They were first identified as disease resistance genes that may play key roles in the cell surface recognition of ligands Plant LRR receptors have been implicated in normal developmental functions as well. (in cell–cell recognition during pollination, in shape and sizeof organs) Brassinosteroid receptor has been identified as an LRR receptor

  9. An example of LRR RLKs Fig. 18.60 Model of a homodimeric receptor-like protein kinase, RLK5, binding its ligand and undergoing autophosphorylation

  10. 3. Receptors with EGF (epidermal growth factor)–like repeat This type of RLK that contains an epidermal growth factor–like repeat has been identified in Arabidopsis. Receptor PRO25 is localized in the chloroplast and interacts with a light harvesting chlorophyll a/b–binding protein (LHCP).

  11. An example of EGF-Like RLK An example of Lectine RLK

  12. Figure 14.24 The MAPK cascade. Hormonal stimulation of the receptor tyrosine kinase leads to the activation of Raf, also known as MAP kinase kinase kinase (MAPKKK).

  13. Fig 18.63 Many signals are transduced by protein kinase cascades that regulate gene expression Siganls: Auxin, GA, ABA, touch, wind, osmotic stress, wounding, elicitor Raf-1L kinase: CTR1 in ethylene signaling

  14. Protein Phosphatase ◆ PP1 ◆PP2A ◆PP2B (calcineurin, CaM-dependent) ◆PP2C: abi in ABA signaling ◆PP inhibitor can prevent red light, proliferation, growth factors, pollen tube signaling Fig18.64 Structure of FK506, rapamycin and cyclosporine.

  15. Fig. 18.65 Ethylene-signaling mutants have striking phenotypes. ETR1: the receptor of ethylene CTR1: negative regulator of ethylene signaling

  16. Fig 18.22 Transgenic plants expressing variants of the etr1-1 gene.

  17. Fig18. 66 Comparison of ethylene signaling pathway and animal Ras-signaling pathway

  18. ABA signaling in plants ABA NO NADPH Oxidase ROS (H2O2) Ca2+ Channel open [Ca2+] ABI1 (PP2C) K+ channel, Cl- channel Reduction of Turgor pressure

  19. Fig 18.71 Some of the known interactions in the plant cell signal transduction network.

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