Midterm 2 Flashcards
How is the G protein composed?
The GPCR and the G protein work together with another enzyme to trigger a transduction pathway
3 different subunits: alpha, beta and gamma, bonded by lipids (heterotrimeric)
What is the phosphorylation cascade?
phosphorylation of serine/ theronine (polar amino acids), activates a series of protein kinases, using ATP tp phorlyate the next, with the final goal of activating a protein
Steps of GPCR?
- ligand binds, shape changes (activates)
- GPCR binds to G protein
- GTP replaces GDP (unbinded), activates G protein
- G protein binds to ligand, changes enzyme shape (activation)
- Cellular response
- GTP hydrolyzed (GDP+Pi, inactive)
How does cholera modify G proteins?
- G protein is modified and unable to hydrolyze GTP to GDP
- The G protein is always activated
- It continuously stimulates the adenylyl cyclase to make lots of cAMP (activates ligan channels)
- The enterocytes secrete large amounts of salts into the intestinal lumen
what are the 2 domains of a transcription factor?
Ligand-binding domain
DNA-binding domain
Glycogen breakdown?
epinerphrine stimulates breakdown of glycogen- glucose 1P
CAMP by adylel cylase converts into AMP, stimulates gylcolysis by activating phosphofructokinase
How is Ca used by the cell?
used by the cell as a second messenger because it is maintained at very low concentration in cell
Ca2+ tend to diffuse very rapidly inside the cell (very high equilibrium potential/current)
What is the specifity of the response?
The response (cellular or nuclear) is specific to the signal and can also differ between tissues and organs for the same signal.
What are scaffolding protiens?
large relay proteins, to which several other relay proteins are simultaneously attached, and that can help to amplify cellular response
Steps in signal transduction pathway (3)
Signal reception: ligand binds to receptor
Signal transduction: conversion of the signal, creaes transduction pathway
Cellular response: the cellular response is specific to the transduced signal
what is Kinase?
enzyme catalyzing the transfer of a phosphate group from ATP to a protein, thus phosphorylating the protein.
What are G protein-coupled receptors?
Cell-surface transmembrane receptor that works with the help of a G protein, which is a protein that binds to GTP, and has a associated enzyme
How can cells communicate (2)
cell junctions
cell-surface molecules (receptors)
Characteristics of GPCRs? (4)
transmembrane domains (7 α helices)
one loop forms a binding sites for the signaling molecules, one loop forms a binding sites for the G proteins
loops are hydrophilic
amino acids in center are non-polar
What is cAMP
second messenger of many biological pathways.i nvolved in epinephrine pathway