P6: Protein Structures

primary structure

sequence/arrangements of amino acids in a polypeptide chain

enkephalin, glutathione, insulin

examples of primary structures

leuenkeohalin, metenkephalin

examples of primary structures

Frederick Sanger

discovered insulin

valine

sickle cell anemia

normal/original: glutamic acid

abnormal shape of the RBC: ?

dehydration reaction

remove h2o molecule, bond is formed

peptide bond formation

• chemically an amide bond, formed via condensation of alpha carboxyl (1) & amino group (2)

• kinetically stable (do not rotate/planar)

• not easily hydrolised w/o an enzyme catalyst

biuret test

determine if a sample has peptide bond (primary structure)

violet solution

what color solution indicates positive result of biuret test.

secondary structure

polypeptide chain fold into a regular repeating structure

pentapeptide (5 amino acids)

give an example of secondary structure

Linus Pauling & Robert Corey

discovered alpha helix & beta pleated sheets in 1951

alpha helix

• rod like structures

• stabilized by H-bonds between CO & NH group of another amino acids, 4 residue apart

proline & glycine

all 20 of the amino acids can fit into an alpha helix except:

proline & glycine

“helix breakers”

alpha helix

INTRAchain H-bonds (within the strands)

b sheets

INTERchain bonds (H-bonds)

b strands

can run in the same direction (parallel b sheets) / opposite directions (anti parallel b sheets)

tertiary structure

• overall course (folding) of a polypeptide chain

• spatial arrangement of amino acids that are far apart in the sequence

myoglobin

it has 153 amino acids and chains folds so that its hydrophobic side chains are burried and its polar charged side chains are on the surface

disulfide bridges

2 cysteine units that combined

• myoglobin

• hemoglobin

• immunoglobulin

• albumin

give an example of globular proteins (spherical)

• collagen

• keratin

• elastin

give an example of fibrous proteins (extended confirmation, less water soluble)

alzheimer’s disease & beta thalassemias

problems in foldings (tertiary structure)

alzheimer’s disease

accumulation of misfolded b amyloid (a protein endogenous to human brain tissues), can lead to severe memory loss or dementia

b thalassemias

• a type of anemia which indicates an absence of chaperone protein ASHP

• precipitation of alpha hgb

alpha hgb stabilizing protein

ASHP means

hemolysis

cytotoxic effects of b thalassemias

quaternary structure

• spatial arrangement of the subunit and the nature of their interactions

• for proteins containing more than 1 type of polypeptide chains

alpha (2)

beta (2)

hgb (4 chains/subunit)

glycosilated hgb

in 1 b chains of hgb, it is where gluc in the blood binds to form a complex, it is called:

HBA1C

most abundant/common GHgb (glycosilated hemoglobin) in the body

HBA1C

monitors glucose control in DM

structural proteins

integral components of tissues & organs inside the body

collagen

most abundant protein inside the body (skin, cartilages)

keratin

structural protein (hair, nails)

elastin

structural protein (dermis, arteries, tendons)

glycoproteins

structural protein (CM)

hemoglobin

transport protein (O2 > cells)

myglobin

transport protein (O2 > muscle tissues)

transFErin

transport protein (iron)

albumin

transport protein (acidic + neutral drugs)

alpha acid glycoprotein (AAG)

transport protein (basic drugs)

casein

nutrient protein: major protein present in milk

ovalbumin

nutrient protein: major protein found in egg (white)

contractile proteins

proteins needed in muscular contractions

actin

contractile proteins: thin & moving filament

myosin

contractile proteins: thick & stationary

cardiac troponins

contractile proteins: muscle contraction in the heart

acute MI

troponin I detected in a blood of a patient means the patient is suspected to have?

hormones

chemical messengers, produces by glands

insulin

• produced by pancreas

• regulate blood glucose levels

somatotropin

“growth hormone” initiates mitosis in the long bones

fibrin

formation of clot

fibrin

fibrinogen is converted into what protective protein?

immunoglobulin (Ig or antibodies)

proteins that protect you when an unwanted substances enters your body

IgG “gamma”

• exposes bacteria to phagocytes

• fixes compliment > lysis

• neutralizes bacterial endotoxin & viruses

IgM

• largest pentamer

• main antibody in the primary response, do not enter the placenta

IgA “alpha”

secretions (luhA, lAway, gAtas) prevents the attachments of bacteria & viruses in the mucous membrane

IgE “epsilon”

mediates immidiate (Type 1) hypersensitivity reactions by causing the releases of mediators from mast cells and basophils

IgD “delta”

found in the surface of b cells where it acts as a receptor for antigens

chromoproteins

color producing proteins

brown

melanin: ___ pigment

red

hemoglobin: ___ pigment (erythrocytes RBC)

enzymes

speed up the chemical reactions inside the body