BIO 320 Chapter Notes - Chapter 15: Sh2 Domain, Structural Motif, Cilium
Chapter 15 Cell Signaling; Cell Signaling I (pg. 822-831)
• Intracellular signaling complexes form at activated receptors
o Scaffold proteins – involved in mechanisms that localize specific interactions in order to
maximize contact with only the appropriate protein partners
▪ Brings together groups of interacting proteins into signaling complexes usually
before a signal is even received
▪ Allows proteins to be in close proximity so they can have more efficient
interactions
o Some signaling complexes assemble only in response to an extracellular signal and
disappear once the signal is gone
▪ Cytoplasmic tail of activated receptor gets phosphorylated and phosphorylated
amino acids become the docking site
• Modular interaction domains mediate interactions between intracellular signaling domains
o Induced proximity – signal triggers assembly of signaling complex
▪ Commonly used to relay signals along a protein pathway
▪ Small interaction domains – found in many intracellular signaling domains
• Vital for assembly of signaling complexes
• Each one binds to particular structural motif in another protein or lipid
o Various types of interaction domains
▪ Src homology 2 (SH2)
▪ Phosphotyrosine-binding (PTB) domains
• Both bind to phosphorylated tyrosines on activated receptors or
intracellular signaling proteins
▪ Src homology 3 (SH3)
• Binds to short, proline-rich amino acid sequences
▪ Pleckstrin homology (PH)
• Binds to charged head groups of specific phosphoinositides produced in
plasma membrane in response to extracellular signal
• Allows proteins to dock and interact with other similar proteins
o Adaptors – links two other proteins together in a signaling pathway
▪ Only has two or more interaction domains
o Interaction domains allow for various combinations of signaling proteins like Lego bricks
▪ I.e. insulin
o Primary cilium – specific region in the cell that concentrates signaling proteins
▪ Projects like an antenna from the surface of most vertebrae cells
▪ Usually short and nonmotile and has microtubules in its core
• Relationship between signal and response varies in different signaling pathways
o Not allows signaling systems work in the same way
o Response timing
▪ Synaptic is very fast, but control of cell fate by morphogens can take days
o Sensitivity
▪ Hormones in low concentration, neurotransmitters in high
▪ Controlled through number or affinity of receptors on the target cell
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