Mammalian cell biology 7

• function of intermediate filaments

  providing mechanical strength and in organising cytoplasmic architecture , signalling and/or regulating transcription 
• what do IF interact with

  microtubules and F-actin
• IF protein subunits

  • domain structure is shared by all IFs
  • broad range of different coiled-coil protein subunits assemble into IFs
  • do not require ATP or GTP for assembly but rather self assemble into an apolar filament
  • coiled-coil contains alpha-helices
  • 2-3 helices wind round each other
  • a-helices are often amphipatic (charged at one side) which serves protein interaction
• what does beta keratin make

  nails, scales and claws or reptiles, feathers, beaks and claws of birds
• what does alpha keratin make

  hair, horns and hooves of mammals
• why are IFs a crucial part of the eye lens

  • 7 types of IFs participate in development and function of the vertebrate eye lens
  • IFs determine the optical properties of the eye lens, they are critical to lens transparency
• properties of septins

  • 13 human septins with >30 isoforms
  • tissue specific expression
  • GTP-binding proteins
  • assemble into oligomers or filaments or bundles
  • interact with membranes
  • roles in cell division, cytoskeleton organisation, membrane remodelling
  • septin-binding proteins control dynamics
• what do septin monomers form

  • spontaneously assemble into core hexamers
  • form oligomers and polymers
• functions of septins at plasma membranes

  • septin ring serves as anchor for proteins that help cell division
  • septin rings at basis of cilia serve as diffusion barriers
  • septin filaments at the plasma membrane provide scaffold for membrane proteins to deform membrane
• what is melanosome motility

  • motors change the colour of fish skin
  • dispersal and concentration depends on kinesin and dynein that move along the microtubules
• structure of kinesin

  usually 2 heavy chains form the motor, associated light chains modify activity or mediate cargo interaction
• what are mechanoenzymes

  protein complexes that utilise ATP to walk along the cytoskeleton 
• what direction does dynein walk in

  minus
• what direction do kinesin and myosin walk in

  plus
• what does golgi depend on

  microtubules and dynein
• what does the ER depend on

  microtubules and kinesin
• why do dynein and kinesin move differently

  • to avoid collisions
  • dynein dances on the microtubule, using several protofilaments
  • kinesin stays on the same protofilament and walks in a straight line