BIOCHEM 2 - PROTEIN FUNCTION Flashcards
Most abundant protein in animals
collagen
SOLUBILITY OF COLLAGEN IN WATER
Water-insoluble fibers
Location of collagen in the cell
extracellular
Has great tensile strength (due to aldol crosslinks)
collagen
contributes to great tensile strength of collagen
aldol crosslinks
major role of collagen
stress-bearing component of connective tissues
location of collagen in body
Cartilage, bones, tendons, ligaments & skin
Primary Structure of collagen
- (-X–Y–G-)-
- X–Pro/Hyp; Y–any aa
- each chain is about 800 aa residues long
Secondary Structure of collagen
- Left-handed α-helix
- 3.3 aa/turn
- Pitch: 10 Å
Tertiary structure
- 3 chains are parallel & wind each other in a right-handed manner to form a triple-helical structure
- H-bond involving Hyp and Hyl residues
- intramolecular and intermolecular aldol covalent crosslinks
Structural proteins
Found predominantly in walls of arteries, lungs, intestines and skins
elastin
“slide & stretch” over one another to maintain structural integrity and provide recoil
Elastin
MW of elastin
MW = 72 kDa;
hydrophobicity of elastin
highly hydrophobic
Connective tissue protein; has elastic properties
elastin
Consists predominantly of nonpolar aa residues, 1/3 G, 1/3 V + A, rich in P
elastin
protein having Random coil conformation
elastin
protein having Intramolecular and intermolecular desmosine crosslinks
elastin
is formed from threeallysyl side chainsplus one unalteredlysl side chain from the same or neighbouringpolypeptide.
Adesmosinecross-link
responsible for the rubber properties of elastin
Adesmosinecross-link
Hemeproteins; conjugated proteins
myoglobin
hemoglobin
Responsible to the red color of the blood
Prosthetic group (non-protein part)
Porphyrin ring
Centrally bound Fe+2
heme
Monomer
Contains a heme
myoglobin
primary structure of myoglobin
1 Structure: 153 aa
secondary structure of myoglobin
2 Structure: Helical
tertiary structure of myoglobin
3 Structure: Globular
Found in skeletal and cardiac muscle
myoglobin
Folded globin chain forms a crevice which encloses a heme group
myoglobin
Heme group of myoglobin is inside the protein since it’s
hydrophobic
Roughly spherical molecule found in red blood cells
hemoglobin
Transport O2 from lungs to every tissue in the body
hemoglobin
Each globin chain of hemoglobin binds a heme group through the______ of a ____________
imidazole ring of a distal histidine residue
Globin of hemoglobin binds the heme at the (site)
5th site – “distal histidine site”
Tetramer: α2β2
Each subunit contains one heme
hemoglobin
each subunit of hemoglobin contains how many heme
1
total of 4 heme
how many heme does hemoglobin have
4
primary structure of hgb
α = 141 aa β = 146 aa
secondary structure of hgb
helical
tertiary structure of hgb
globular
quaternary structure of hgb
4 folded chain in tetrahedral arrangement
O2 and CO2 have different binding sites
Oxyhemoglobin
Carbaminohemoglobin
Carboxyhemoglobin
Methemoglobin
Decrease in pH causes
2
release of O2 and converts oxyhemoglobin to deoxyhemoglobin.
Genetically altered hemoglobin
sickle cell anemia
in sickle cell anemia which aa is defective
6th aa of β subunit
Glu Val
Regulatory proteins
Endocrine hormones
INSULIN & GLUCAGON
responsible for carbohydrate homeostasis
INSULIN & GLUCAGON
Produced from β-cells of Islets of Langerhans
INSULIN
regulatory protein with 2 polypeptide chain
(51 aa residues)
INSULIN
protein having
Intermolecular and intramolecular disulfide linkage
INSULIN
Hypoglycemic hormone
INSULIN
linkages found in insulin
Intermolecular and intramolecular disulfide linkage
Produced from α-cells of Islets of Langerhans
glucagon
Single polypeptide chain
(29 aa residues)
glucagon
Involved in increasing the blood levels of glucose
glucagon
how many aa residues are in a single polypeptide chain of glucagon
29 AA residues
how many aa residues are in insulin
51 AA residues
DISEASES RELATED TO INSULIN
Hypoglycemia
Hyperglycemia
Diabetes mellitus
Defense proteins
Also known as antibodies
immunoglobulins
secrete antibodies
B lymphocyte:
is a protein that is produced by the body in response to an “invading” (foreign) substance.
An antibody
- are produced as part of the body’s immune response to protect itself.
An antibody
is the substance that the body is trying to “fight off” (eliminate or reduce) by mounting an immune
response
antigen
Y-shaped molecule
Tetramer
immunoglobulins
linkages found in immunoglobulins
Interchain and Intrachain disulfide linkages
chains of immunoglobulins
Light Chain
Heavy Chain
regions of immunoglobulins
Constant Region
Variable Region
Antibody that is commonly found in human secretions like tears, mucous and saliva
IgA
Cell attached antibody which function is still under study
IgD
Antibody responsible for allergic reactions
IgE
Most dominant antibody in humans. This antibody is responsible for secondary immune response
IgG
The antibody which serves as protection for primary infections
IgM
DISEASES related to immunoglobulins
Autoimmune Diseases
Inherited Immunodeficiency
HIV
In what oxidation state must the iron atom be for the heme to bind oxygen
Fe (II), +2
Which type of hemoglobin binds more tightly to oxygen, fetal or adult?
Fetal
is hemoglobin an allosteric enzyme
yes
the affinity of fetal hemoglobin for oxygen is higher than
that of maternal hemoglobin
