BGM1002/L04 Non-Globular Proteins Flashcards
Name 3 structural proteins.
Keratin
Silk
Collagen
Name a fibrous/filamentous protein.
Cytoskeletal proteins
Name 3 globular proteins that assemble into fibrous quaternary arrangements. (3)
Cytoskeletal proteins
Flagellae
Pilli
Filamentous viruses
Give 3 features of protein fibres.
Strong
Dynamic
Can interact with other proteins in DNA
Why don’t bacteria need a cytoskeleton for shape?
Their cell wall provides their shape.
Give 3 functions of the cytoskeleton.
Links membrane to nucleus in eukaryotes
Provides mechanical stability
Provides template for cell wall construction in some organisms
Give the 3 components of the cytoskeleton.
Microfilaments
Intermediate filaments
Microtubules
What are microfilaments primarily made from?
Actin
How does actin contribute to the function of microfibrils?
Actin binds and hydrolyses ATP
Which end does actin 1) bind at and 2) dissociate at?
1) Positive end
2) Negative end
Which proteins (2) sequester free actin?
Profilin & gelsolin
Name 4 features of intermediate filaments.
Long
Strong
Elastic
Flexible
What are intermediate filaments formed from?
Long coiled-coil proteins that may have globular ends at termini
Give 3 functions of intermediate filaments.
Cell adhesion
Cellular organisation
Muscle fibres
What type of intermediate filaments are keratins?
I & II
Name the 2 Type III intermediate filaments.
Vimentin & Desmin
Name the 2 Type IV intermediate filaments.
Alpha-internexin & synemin
Name the Type V intermediate filament.
Lamins
Name the 2 Type VI intermediate filaments.
Nestin & Filensin
Describe the structure of Keratin.
Superhelices formed by coiled coils
Name 5 structures made from alpha-keratin.
Hair
Skin
Claws
Nails
Feathers
Name 3 structures made of beta-keratin.
Scales
Nails of reptiles
Tortoise shells
How is keratin’s coiled-coil structure stabilised?
Hydrophobic interactions
How is keratin formed?
Dimers multimerise to form tetramers and so on, to produce filaments.
Describe the structure of Vimentin.
Coiled coil of eight tetramers, stuck together to form fibrous filaments
How is Vimentin formed?
Dimerisation and formation of antiparallel tetramer
What is the function of Vimentin?
Anchors organelles in cytoskeleton
Name the 2 key proteins of neurofilaments.
Alpha-interexin & nestin
Describe the structure of Lamin (3).
Long alpha-helix with one globular domain present
Polymers organised into protofilaments
Coiled-coil domain and terminal head
What is the function of Lamin? (2)
Structure and regulation of nucleus
Feedback to cell on mechanical stress
What are microtubules composed of?
Alpha and beta tubulin.
What charge does 1) the beta end and 2) the alpha end of microtubules have?
1) Beta +ve
2) Alpha -ve
What end does elongation occur more rapidly in microtubules?
Beta/ positive end
How many protofilaments form a helical filament in microtubules?
13
What does MTOC stand for?
Microtubules Organising Centre
What is the key MTOC in the cell?
Centrosomes
What does the drug Taxol do?
Inhibits cell cycle & stabilises GDP-bound tubulin
Cancer drug
What is the function of microtubule-related proteins?
Regulate microtubule stability
What do molecular motors do (2)?
Traffic vesicles in cells
Endo-exocytosis
What proteins are present in muscle fibres? (5)
Actin
Myosin
Troponin
Tropomyosin
Titin
What is special about the protein Titin?
Biggest known protein
Prevents over-extension
What is the singular protein subunit in flagellae?
Flagellin
Name an example of a filamentous virus.
Filamentous bacteriophage
Tobacco Mosaic Virus
Some influenza viruses
What kind of structure protects genetic material in filamentous viruses?
Helix
What is the function of pilli?
Cell-cell recognition for transfer of genetic information
What protein do pilli consist of?
Pillin
Describe the structure of pillin.
Globular domain with long alpha-helix filaments
What is the diameter of pillin’s helical arrangement?
6-7 nm
What are fimbriae?
A surface attachment/ hair-like extension on some archaea and bacteria
What are curli fibres?
Amyloid fibres produced by enterobacteria
What structure does collagen consist of?
Triple helix of 2 a1 chains and 1 a2 chain
What 3 amino acids is collagen rich in?
Glycine, proline and hydroxyproline
Give two examples of diseases related to collagen-deficiency.
Scurvy
Ehlers-Danlos
Epidermolysis bullosa
Give 2 examples of animals that produce silk.
Silkworm
Hymenoptera (bees, wasps, ants)
Spiders
Lacewings
What percentage of fibroin and sericin does silkworm silk contain?
70-80% fibroin
20-30% sericin
Give 2 general properties of spider silk.
Highly ductile
High tensile strength
Describe the structure of spidroin.
Repetitive glycine and alanine rich blocks
Beta-strand regions with disordered regions
Give 3 types of spidroins.
MaSp1
MaSp2
Flagelliform
What type of proteins don’t have regular tertiary structures?
Intrinsically disordered proteins
Give 3 examples of diseases caused by misfolded proteins/accumulation/aggregation.
Alzheimer’s
Parkinson’s
ALS
CJD
Type II diabetes
What 3 proteins are most susceptible to misfolding?
Alpha-synuclein
Beta-amyloid
Prion
What kind of dye is used for amyloids?
Congo red dye