Phosphorylation – Modes of Cell Communication

by Georgina Cornwall, PhD

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    00:00 Before we do that, we need to consider the concept of phosphorylation. I've introduced already the idea that ATP is the energy currency molecule. So we phosphorylate or add phosphates to ATP in order to make it high energy and then we can release energy from this energy currency molecule by removing a phosphate. Similarly we can phosphorylate proteins. And this can either act as a deactivator or activator of a signal transduction pathway. So it can literally turn a process on or it can turn a process off.

    00:41 Sometimes we add a phosphate to turn a process on or turn a protein on to activate a signal transduction pathway.

    00:48 And sometimes the phosphorylation, on occasion, will end up phosphorylating a protein that shuts the system down.

    00:56 Most often it's an activator though. So again to review how ATP is formed. We take an adenosine diphosphate, we add a little bit of energy, and the phosphate molecule is attached. And then we can dephosphorylate, remove the phosphate. Release some energy that's usable to run our bodies system or cellular processes and form ADP. So this is an ongoing cycle. And we'll visit it many other times throughout this course.

    01:27 So just as we could phosphorylate ADP and make it ATP, we can also phosphorylate proteins. And this is what happens a lot in our signal transduction cascades in order to elicit cellular effects. So in this case we have a protein kinase perhaps and ATP or perhaps even GTP might come in and drop off a phosphate and attach it to the protein and itself leave as ADP. So we've now phosphorylated some sort of protein.

    02:02 Could be a protein kinase and we'll be examining many of those in the future of this lecture.

    02:07 So, once we have a protein phosphorylated, it could actually go and activate a cascade, a signal transduction pathway. Or it could run off and shut down something. So maybe this protein grabs on to another protein and prevents it having its action. So phosphorylation could result in either a positive effect on the signal transduction or a negative effect. Shutting down effect of signal transduction.

    02:41 These proteins can also be dephosphorylated, right. Removing the phosphate group. And the enzyme that removes the phosphate group would be called protein phosphatase. -ase again is an enzyme.

    02:54 So it's going to remove the phosphate so that that phosphate could be recycled and added perhaps to another protein. Generally the molecule that's going to add phosphates is ATP.

    03:06 However we will also see GTP coming into play because we have this G-protein modulated responses.

    About the Lecture

    The lecture Phosphorylation – Modes of Cell Communication by Georgina Cornwall, PhD is from the course Cellular Structure.

    Included Quiz Questions

    1. The signal transduction pathway in cell communication
    2. The external environments of the cell
    3. The extracellular concentrations of the electrolyte molecules
    4. The extracellular fluid volumes
    5. The bonding and branching patterns in the amylose macromolecule
    1. Counteracts the protein kinase action by dephosphorylation of the proteins
    2. Assists the protein kinase activity by phosphorylation of the proteins
    3. Assists the protein kinase activity by joining amino acids to form fully functional proteins
    4. Participates in the phosphorylation of ADP to generate ATP
    5. Assists the protein kinase action by breaking down the proteins into amino acids

    Author of lecture Phosphorylation – Modes of Cell Communication

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD

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