arrangement of microtubules is lost and replaced by mitotic spindle - overlapping of microtubules
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Plus end microtubule binding proteins (+TIPS)?
EB-1: Only binds GTP-tubulin (when bound in a microtubule) - stabilises the MT seam. DASH ring complex: Binds polymerising and depolymerising MTs : couples kinetochore movement to MT depolymerisation (fungi only)
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Cross-linking, stabilising or bundling proteins?
MAP2, Tau: Binds side and stabilizes parallel MTs. MAP65 (Ase1): Binds side and stabilizes anti-parallel MTs
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Describe the Dam1/DASH complex structure?
The purified heterodecameric complex is T-shaped and can link together to form chains. In vitro the complex can form rings around purified microtubules. The ring is composed of 16 heterodecamers with gap of 75A between the outside of MT & inside ring
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role of curling of microtubules?
when microtubule disassembles, positive disassembling end gather up the ring complexes and they accumulate, unable to fall off the end due to the curling
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What are the Tau class proteins?
MAP2 and Tau itself bind via a positively charged tail which binds the negatively charged surface of the lattice
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Where is MAP2 found and what does it do?
. MAP2 is only found in dendrites where it forms fibrous cross-links between MTs and intermediate filaments
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Wher is Tau found and what does it do?
Tau is found in dendrites and axons and acts as a bridge between parallel MTs
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What does MAP65 do?
bundles and stabilises antiparallel microtubules
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Describe kinesins
14 structurally related classes. Includes those that can either stabilise, de-stabilise or bundle MTs. Kinesins are mostly plus end directed (=walk towards plus end) motors but some(such as kinesin-14)are minus end directed.Use ATP to generate force
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Describe dynein
Fast minus end directed motor. Structurally unrelated to kinesins. Use ATP to generate force
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How do motor proteins for microtubules (kinesin and dynein) move?
'step' in holes betweeen the alpha and beta tubulin dimers
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kinesins do what?
Direct exocytosis (carry cargo towards the plasma membrane)
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Dynein does what?
directs endocytosis (carry cargo away from the plasma membrane) 100x faster than kinesin
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describe regulated melanosome movements in fish pigment cells
the pigment granules aggregate or disperse depending on the concentration of cAMP in the cell (through the action of cAMP-dependent protein kinase).
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How does kinesin 'walk'?
forward motor binds beta-tubulin releasing ADP -> forward head binds ATP -> conformational change in neck linker causes rear head to swing forward -> new forward head releases ADP, trailing head hydrolyses ATP and releases Pi
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How does the structure of dynein help it move?
. A single heavy chain consists of a stem, to which dynactin binds, a head domain containing the ATPase which generates the force for movement and a stalk domain which protrudes from the ATPase wheel .
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How is the structure of dynactin useful for dynein?
contains 11 proteins. Key to this structure is 8 copies of Arp1 (an actin related protein!) which forms a mini actin-like filament that is responsible for cargo binding & is is capped by CapZ and linked to p150Glued by dynamitin.
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Structure of centrosome
composed of two centrioles (composed of 9 pairs of short stable triplet microtubules) (a mother and a daughter) surrounded by pericentriolar material (matrix) to which g-tubulin containing MTOCs are associated
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Structure of doublet/triplets MTs found in specialised structures?
contain an A tubule, which has 13 protofilaments and a B tubule (in doublets) or a B and C tubule (in triplets) which have either 10 or 9 protofilaments, respectively
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Other cards in this set
Card 2
Front
Plus end microtubule binding proteins (+TIPS)?
Back
EB-1: Only binds GTP-tubulin (when bound in a microtubule) - stabilises the MT seam. DASH ring complex: Binds polymerising and depolymerising MTs : couples kinetochore movement to MT depolymerisation (fungi only)
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