The Cytoskeleton
Intermediate Filaments 8-10 nm in diameter Four types: basis of aa sequence actin & tubulin -> globular protein, cell type specific subunit of IF -> fibrous protein, wide range of size, nonpolar Around nucleus, extend out to cell periphery (by attachment of ut) Abundant in cells require mechanical stress: epithelia, length of axon, cytoplasm of smooth muscle
Epidermolysis bullosa simplex
Amyotrophic lateral sclerosis (Lou Gehrig’s Disease) : accumulation and abnormal assembly of NF in motor neuron cell bodies and in the axon -> interfere axonal transport -> degeneration of axon -> muscle weakness and atrophy
A microtubule array can find the center of a cell Dynamic + ends pointing outward and stable - ends collected the center
Dynamic instability
Effects of stathmin on microtubule polymerization
Organization of microtubule bundles by MAPs
The effects of proteins that bind to microtubule ends
Capping proteins help to localize microtubules
Microtubule motors Dynein Kinesin
Microtubules in cilium or flagellum
Ciliary dynein
The bending of an axoneme
Basal bodies
Kinesin and KRP
A model for the attachment of dynein to a membrane-enclosed organelle
Actin filaments
The tip of the leading edge of a cell nucleates actin filaments
Nucleation by the ARP complex
Web formation by the ARP complex
Actin Binding Proteins
Profilin bound to an actin monomer
Effects of thymosine and profilin on actin polymerization
Filament capping and its effects on filament dynamics
Actin array in a cell
Actin-cross-linking proteins
The formation of two types of actin filament bundles
A microvillus
Filamin cross-links actin filaments into a 3-D network with the physical properties of a gel
Filament severing and its effects on filament dynamics
A model for actin filament severing by gelsolin
Platelet activation
The role of ERM (ezrin, radixin, moesin)-family proteins in attaching actin filaments to the plasma membrane
Focal contacts and stress fibers in a cultured fibroblast
The effects of Rac, Rho, and Cdc42 on actin organization in fibroblasts
The Actin motors Myosin
Myosin II
The Myosin II bipolar thick filament
The motor activity of the myosin head
Myosin superfamily tree
Comparison of the domain structure of the heavy chains of myosin types
Light-chain phosphorylation and the regulation of the assembly of myosin II into thick filaments
Skeletal muscle myofibrils
Organization of accessory proteins in a sarcomere
T tubules and the sarcoplasmic reticulum