protein binding, constants, and insulin

what are the different functions of proteins

enzymes (enzymatic functions)

chemical messengers

buffer support

transport

immune response (antibodies)

energy (need lots bc u don’t want a protein deficit)

what do structural proteins do

provide structure and support for cells (cytoskeleton and skin)

ex: collagen/elastin, keratin, actin/myosin, and tubulin

what are the chemical messenger proteins

hormones and cytokines

what are hormones and what do they maintain

they are produced by the endocrine glands in the body and help maintain metabolism, sexual function, circadian rhythm, mood, electrolyte balance, and body temperature

what are cytokines

they are produced mostly by your immune cells and other cells that make up the rest of the immune system which help to keep your immune system properly functioning

what are the size and some examples of cytokines

they are small proteins that are 5-25kDa

some examples are interferons (IF), interleukins (IL), and tumor necrosis factor (TNF)

what are some other examples of hormones

they are modified amino acids that trigger responses that increase focus, anxiety, alertness, blood flow, etc.

some examples are dopamine, norepinephrine, and epinephrine

what is the peptide hormone

oxytocin: nonapeptide (9 amino acids) known as the love hormone

what is protein binding

a reversible non covalent interaction where a molecule called a ligand attaches to a specific region on a protein (the binding site) to carry out a biological function.

what is insulin

it is the main anabolic hormone of the body produced by the pancreas that is 51 amino acids long (smaller proteins)

what does insulin do

it regulates the metabolism of carbohydrates, fats, and proteins and promotes the absorption of glucose from the blood into the cells of the body

what is a ligand

anything that binds to a receptor

what is the insulin receptor

tyrosine kinase

what does binding of insulin to the receptor do to the conformation

it changes the conformation from V shape to T shape

what does the conformation change of the tyrosine kinase receptor do

it causes the autophosphorylation of the tyrosine residues on the receptors cascading the phosphorylation and activation of other proteins/enzymes

what is the the protein ligand complex

• The combined unit formed when the protein and ligand reversibly bind together via non-covalent forces (hydrogen bonds, ionic bonds, hydrophobic interactions): P + L ⇌ PL

what is the Ka

it is the association constant or Kon (2)

what is Kd

it is the dissociation constant or Koff (1/2)

equilibrium association constant

Ka protein = [PL]/[P] [L] or ka/kd

what happens to the protein complex with a high Ka and low Kd

complex wants to stay together

what happens to the protein complex with a low Ka and high Kd

the complex doesn’t want to stay together, each wants to get rid of each other

what is the equilibrium dissociation constant formula

Kd protein = [P] [L] / [PL]

association constants units

K_a(protein) has units of M^-1

dissociation constant unit

K_d(protein) has units of M

association constant formula and inferences

•Ka protein=[PL]/([P][L])

•A high association constant  indicates a strong binding affinity.

A low association constant indicates weak binding affinity

dissociation constant equation and inferences

•Kd protein=[P][L]/([PL])

•A high dissociation constant  indicates a weak binding affinity.

•A low dissociation constant indicates strong binding affinity.

why do we use dissociation constants

•We use dissociation constants because they can be expressed in concentration units (M).

•It is the concentration at which half of the proteins have bound the ligand.

•The lower the concentration to reach this threshold, the higher the affinity a protein has for its ligand.

•The higher the concentration to reach this threshold, the lower the affinity a protein has for its ligand.

dissociation constant what is it/formula/what it represents

• What it is: The equilibrium constant that measures the tendency of the protein-ligand complex to break apart into its separate components.

• Mathematical formula: Kd = [P][L]/[PL] (or the reciprocal of Ka

• What it represents: A lower Kd means tighter binding (the complex stays together easily), while a higher Kd means weaker binding (the complex dissociates readily).

association constant what is it/formula/what it represents

• What it is: The equilibrium constant that measures the tendency of a protein and ligand to bind together.

• Mathematical formula: Ka = [PL]/[P][L]

• What it represents: A higher Ka means a stronger, tighter, and more favorable binding affinity between the protein and the ligand.

mathematical relationship of Ka and Kd

• They are inverses of one another:

• Ka = 1/Kd and Kd = 1/Ka
  

• Numerically, Kd is equal to the concentration of free ligand at which 50% of the protein's binding sites are occupied.