CellBio_Lecture7_ActinCytoskeleton.docx

1114 a gtp remnant model for rescue model for

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11.14 A GTP remnant model for rescue Model for microtubule dynamics showing GTP-tubulin (red) in GTP cap during polymerization (P) and in inner microtubule regions. Such inner microtubule regions that contain GTP-tubulin is known to exist. Upon loss of GTP cap (C), catastrophe occurs and the microtubule deploymerizes (D) until its end reaches a GTP-tubulin remnant. A GTP capped end is restored and polymerization occurs resulting in rescue (R) 11.15 The end of a microtubule can grow and shrink even under constant alpha/beta tubulin concentration > dynamic stability The average behavior of a large number of microtubule ends can be defined by: rate of assembly (prop. to [tubulin]) rate of disassembly (indeed. of [tubulin]) frequency of catastrophe (inv. prop. to [tubulin]) frequency of rescue (prop. to [tubulin]) 11.16 Dynamic instability allows microtubules to probe the 3-dimensional space inside a cell. Lecture 5 coated recruitment shows SAR1 and ARF etc. STOP HERE FOR EXAM (through all of lecture 11) pop quiz: (attendance only) alpha actinin is an f actin protein present at the Z (cap? or something) you to this wrong! LECTURE 12
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12.1: Regulators of Microtubule / Microtubule Based Motility 12.2 Many proteins affect the dynamic properties and functions of microtubules in a living cell. here are just some examples - don’t memorized the figure. Stathmin Kinesin-13 MAP2 tau plectin MAPs XMAP215 +TIPs centrosome gamma-TuRC 12.3 In most animal cells, the minus end (at MTOC) of most microtubules is NOT free. Examples of microtubule organizing center (MTOC) centrosome in animal cells an basal body in some animals with cilia or flagella. Plant cells are unique in that they have no well defined MTOC. Important for cell signaling. 12.4 The centrosome is the major microtubule organizing center of animal cells and is found near the cell center next to the nucleaus in most such cells Microtubules are nucleated from a large number (>50) of gamma tubulin ring complexes at the centrosome. 12.5 Pair of centrioles (arranged at right angles to each other) are important parts of the centrosome (but not all MTOCs have centrioles) 9 Triplet Mts each triplet has 13+10 + 10 protofilaments (cylinder of cylinders) 9 molecules of SAS-6 dimers form a cart-wheel structure to organize the triplets SAS6 looks like a motor protein because of its “arms” but it is not a motor protein. It helps form the cartwheel structure seen on this slide.. Holds each triplet in place. In most cell types centrosome is near the center of the cell and the golgi is also present there. negative end of microtubule near centrosome positive plus end extends towards cell membrane ARP complex has actin like domains, a surface that looks like the end of an actin filament (plus end) hence three subunits can add and continuously assemble. ARP nucleating. similar to how gamma tubulin is nucleating.
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  • Spring '09
  • BUSHART
  • Microtubule

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