23/11/18
Dr John Connelly
The Cytoskeleton
• Network of interconnected filaments and tubules
• Polymers
• Dynamic
Functions
• Cell structure and mechanics
• Force generation and motility
• Intracellular transport
• Cell division
• Makes up most of the cell
1. Microtubules
• Heterodimers of α and β tubulin proteins
• Wrap around to form 25nm wide tube, with a 15nm lumen
o This gives polarity
• Largest element
1. Cytoplasmic
▪ For structure and division
▪ Acts as a track
▪ Regulates shape and vesicle transport
▪ Important for long neurons
▪ Usually a singlet
2. Axonemal
▪ Motility
▪ In flagella
▪ Signalling hub attached to basal body
▪ Doublet or triplet
▪ 9x2 formation
• Polymerisation
1. Nucleation – coming together
2. Elongation
3. Plateau – treadmilling (some added, and some removed in equilibrium state)
• Microtubule growth is concentration dependent, and add more efficiently at the plus end
Critical concentration = tubulin concentration where assembly and disassembly is balanced
Polarised growth
End Tubulin Concentration Growth
Plus High Rapid
Plus Low Slow
Minus High Slow
Minus Low Shrinkage
Dr John Connelly
The Cytoskeleton
• Network of interconnected filaments and tubules
• Polymers
• Dynamic
Functions
• Cell structure and mechanics
• Force generation and motility
• Intracellular transport
• Cell division
• Makes up most of the cell
1. Microtubules
• Heterodimers of α and β tubulin proteins
• Wrap around to form 25nm wide tube, with a 15nm lumen
o This gives polarity
• Largest element
1. Cytoplasmic
▪ For structure and division
▪ Acts as a track
▪ Regulates shape and vesicle transport
▪ Important for long neurons
▪ Usually a singlet
2. Axonemal
▪ Motility
▪ In flagella
▪ Signalling hub attached to basal body
▪ Doublet or triplet
▪ 9x2 formation
• Polymerisation
1. Nucleation – coming together
2. Elongation
3. Plateau – treadmilling (some added, and some removed in equilibrium state)
• Microtubule growth is concentration dependent, and add more efficiently at the plus end
Critical concentration = tubulin concentration where assembly and disassembly is balanced
Polarised growth
End Tubulin Concentration Growth
Plus High Rapid
Plus Low Slow
Minus High Slow
Minus Low Shrinkage
