1
Q
Phosphorylation, Acetylation
A
- alters stability/ signalling
2
Q
Glycosylation
A
- affects protein folding
- secreation
- solubility
- binding to other biomolecules
3
Q
Myristolyation, farnesylation
A
- alters location
4
Q
Lipoproteins
A
- binds lipids
5
Q
Metalloproteins
A
- bend metal ions
6
Q
Hemoproteins
A
- have an attached heme group
7
Q
Examples of Covalent Modifications of Proteins
A
- can change protein funtion
1. linking a fatty acid to the side chain of a cys
2. adding a sugar to the side chain of an asn
3. adding a phosphoryl group to a ser side chain
8
Q
Protein-ligand Binding
A
- assume binding is reversible
- proteins contain sites which ligans specifically bind and form a “complex” with a protein
- binding occurs by multiple weak + a few strong forces (leads to specificity)
9
Q
Dissociation Constants
A
- high affinity = tight binding = small Kd
10
Q
Myoglobin
A
- consits of 8 alpha helices plus 1 heme prosthetic group
- oxygen-binding protein
- facilitates oxygen diffusion through tissues
(transports O via the Fe in heme)
11
Q
Hemoglobin
A
- complicated with 4 subunits ( 2 aplha, 2 beta)
- each subunit has a heme group
- similar to myoglobin in their secondary/ tertiary structure
12
Q
2 States of Hemoglobin
A
- Deoxy
- Oxy
13
Q
Deoxy State
A
- t state (tense)
- low affinity
- cannot find oxygen very well
14
Q
Oxy State
A
- r state (relaxed)
- high affinity
15
Q
Structure Proteins Collagen
A
- most abundant protein in animals
- form strong/insoluable fibers in extracellular matrix
- connects + strengthens tiessues
- 28 members in the collagen protein family
- have characteristic triple-helical structure
- job: give support to animals/ strengthen bones
16
Q
Characteristics of Collagen’s Primary Structure
A
- every 3rd residue is glycine
- lots of proline/ hydroxyproline
- some proline residues are hydroxylated after the protein has been synthesized
- consists of repeating triplets (Gly- Pro- Hyp)
- contain Lys residues that are chemically modified after protein synthesis
17
Q
Hydroxyproline
A
- modified form of proline
- requires enzymes to add hydroxyl group to promine
18
Q
Proline Hydroxylation
A
- a type of post-translational modification
19
Q
Collagen Properties
A
- thin (1.5 nm)
- long (300nm)
- very strong molecule
- hydrophobic/ insoluable (due to many exposed hydrophobic side chains)
20
Q
Collagen Forms a Triple Helix
A
- repeating Gly-Pro-hyp triplets form a stable left-handed helical structure
- 3 collagen polypeptides wind around eachother to form a right handed triple helical structure
- N-H group of glycine forms an H-bond with the C– O group of a residue on a neighbouring chain
21
Q
Collagen Synthesis and Assembly
A
- pro-collgen secreted from cell (propeptides don’t form triple helical structures)
- pro-peptides removed before fabril assembly (pro-peptidase enzymes oresent outside cells)
- collagen molecules are covalently cross-linked in the fibril
22
Q
Collagen Synthesis
A
- glycosylation facilitates extracellular soluability as well as water absorption
23
Q
Hydroxylysine
A
- OH groups serve as sites of sugar addition
24
Q
Cross- Linking
A
- between chemically modified lysine residues in collagen
25
Collagen Related Disease
1. Scurvy
2. Osteogenesis Imperfecta
26
Scurvy
- vitamin c deficient
- lact of vitamin c (ascorbate acid) in diet
- vit c is needed for enzyme that hydroxylates proline
- non-hydroxylated prolines = unstable collagen
27
Osteogenesis Imperfecta
- "bad bone"
- some due to the replacement of glycine by other amino acids
- prevent proper assembly of triple helix
- leads to lack of collagen
- bone fragility and deformation
Biochem 2280
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