1. Chapter 2: Protein Interactionspp

2. Let’s look at how proteins interact

3. Proteins as: Proteins as: Enzymes Transporters Signals Receptors
Binding proteins
Regulatory proteins
Immunoglobulins

4. An enzyme at work
CARBONIC ANYDRASE
CO2 + H20
H2CO3

5. Protein transporter (one example there are many more!)

6. Cell Signaling through various processes will be discussed in detail in chapter 5)
Ligand and receptors
Why do we care??
Normal Cells respond to cell signals!
And Abnormal cells respond to cell signals!!

7. Equilbrium Constant Keq
Keq=[P][L]\[PL]
Refers to the ratio of bound ligand verus unbound ligand
Quantitative expression Keq is called dissociation constant or Kd.
What would a “large Kd value” tell you about a drug versus a “drug with a smll Kd value”?

8. Chapter 2: Protein Interactionspp

9. Isoforms of hemoglobin
Fetal hemoglobin has lower Kd for O2 than adult hemoglobin.
What does this mean physiologically?

10. Ligands can sometimes mimic another ligand for a protein.
Nicotine
Acetylcholine

11. Proteins as Immunoglobulins

12. Protein Binding to a substrate (ligand)
Can be affected by:
Cofactors interacting with the protein
Proteolytic activation of the protein
Modulators (there are different modulators)
Protein: for example an enzyme
Substrate/ligand

13. Cofactors: enzymes may have requirements in order to work…

14. Cofactors: non-organic
For example: Mg++, Ca++, Cl-
May be required for enzyme activity!
and Co-Enzymes!

15. Proteolytic activity of a digestive enzyme

16. Competitive inhibitor is an example of a “reversible modulator”

17. Example of Reversible antagonist
Ritonavir: protease inhibitor

18. However some Modulators ar irreversible inhibitors
Tamoxifen and breast cancer treatment
For example: penicillin

19. Most enzymes have modulators to be optimally active…
Modulators assist in providing ideal conformation for reactions

20. Figure Overview

21. Covalent Modulation Kinase activity (exchange reaction)
Phosphatase activity
(remove group reaction)

22. pH and temperature

25. We regulate the amount of protein made:

26. The body regulates the…
Amount of proteins we make (example)
Glucagon increases blood glucose
Insulin decreases blood glucose
Up regulation
GLUCAGON
Down regulation
INSULIN HOMEOSTASIS 

27. FOR EXAMPLE
GLLUCOSE
Figure 2-23