Tertiary structure Flashcards
what are Fibrous proteins
- Scleroproteins
- 2° structures form long parallel fibres and sheets
- Usually insoluble
what are the two types of fibrous proteins important for support and strength
- Collagen
* Keratins
give example in where alpha and beta keratin are found
- α-keratins
- Mammalian hair and nails
- B-keratins
- Invertebrate silks, reptile claws, scales and shells
- Avian feathers, beaks and claws
Collagen structure and properties
- Superhelices of glycine-rich α-helices
- Main protein of connective tissue
- Most abundant protein (25% of total protein)
- Strong and elastic
α-Keratins: Hair and nails structures and properties
- Composed of coiled-coils of two α-helices that assemble together into larger fibres
- Strong and inextensible
- Insoluble and chemically inert
- Disulphide bridges cross link coiled coils
beta-Keratins: Fibroin structures and properties
- Fibroin is found in silk cloth and spider webs
- Layers of anti-parallel β sheets rich in Ala and Gly residues
- Small side chains interdigitate and allow close packing of the sheets
- Great strength
- Sheets joined by amorphous stretches which confer elasticity
what are Globular Proteins properties
• Mixture of irregularly folded secondary elements to form a compact 3-D spherical shape
- Usually soluble with inner hydrophobic core
- Transported easily in body fluids
- Important functions in cell chemistry
examples of Globular Proteins?
- Myoglobin
- Haemoglobin
- Immunoglobins
where is it found Myoglobin and what is its structure
oxygen
porphyrin and fe+2
histidine
what are Quaternary Structure
- Assembly of subunits (separate polypeptide chains) of multimeric proteins
- Enabled by van der Waals interactions
structure of Haemoglobin A
• Tetramer
- 4 chains/subunits (α2, beta-2)
- 4 haem molecules (porphyrin and Fe2+)
how do these diseases arise
- Sickle Cell Anaemia
- beta-chain mutation (Glu to Val)
- Thalassaemia
- Underproduction of globin chains (genetic)
- beta-thalassaemia (beta-chains decrease )
- α-thalassaemia (α-chains decrease )
• Porphyria
- decreased Haem production (defects in synthetic pathway)
- Photosensitivity, hirsutism and discolouration
what are Immunoglobulins
• Y-shaped proteins (antibodies) used by the immune system to identify and combat non-self
- 4 chains linked by disulphide bridges
- 2 large H (heavy) chains
- 2 short L (light) chains
- Chain tips have a variable structure
- Chain tips form specific binding sites for non-self targets (antigens)
- Antigen recognition by an antibody tags it for attack by other parts of the immune system
Some proteins tend to aggregate into non-functional structures during assembly
what is a Chaperone proteins
• Chaperone proteins assist the non-covalent folding/unfolding of a protein
Chaperone protein functions
- Prevent aggregation into non-functional units
- Repair misfolded/heat damaged units
- Require ATP for energy to assist folding
- Chaperonin is a type of chaperone
