KINE 1000 Lecture Notes - Lecture 4: Desmosome, Intermediate Filament, Alpha Helix
4 Jun 2018
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Iterediate Filaets
• 10nm thick. Rope-like fibers span the cell for mechanical strength
• Found in neurons, epithelial cells & meshwork of nuclear lamina
• Intermediate filaments form a cytoplasmic filament in vertebrates, nematodes &
mollusks
• Iterediate filaets are proiet i ytoplas of ells that’re sujet of
mechanical stress & not found in animals that have rigid exoskeleton like
arthropods. Give mechanical strength to tissues in squishier animals
• Intermediate filaments are more diverse & encoded by 70 different human genes
w/distinct cell type-specific functions
Intermediate Filament Structure
• Subunit = alpha- helical monomer
• Alpha helical monomer < coiled-coil dimer < staggered tetramer < 8 tetramers in
filament
• No binding of ATP or GTP
• No polarity of filament
• Assembly involves phosphorylation
• Different types of filaments. Can be dynamic in cells, others form stable
structures
• Amino & carboxyl-terminal domains differ. Intermediate filaments are elongated
proteins w/conserved central alpha-helical domain that form coiled-coil structure
with another monomer. A pair of parallel dimers associate in antiparallel fashion
to form a staggered tetramer. Tetramer is four polypeptide chains
• Iterediate filaets do’t have idig site for nucleotide like actin or tubulin
• Tetrametic subunit is made of two dimers pointing in opposite direction.
Assembled intermediate filament lacks structural polarity.
• Tetramers pack laterally to form filaments- 8 parallel protofilaments made of
tetramers. Thus each intermediate filament has 32 individual a-helical coils (16
dimers). Half dimers are pointing in one direction
• Intermediate filaments have strong lateral hydrophobic interactions, bends
easily.
• Intermediate filaments are stable due to tight associations of subunits. Some
intermediate filaments like vimetin are highly dynamic structures in cells like
fibroblasts
•
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