Cytoskelet.

Prezentace na téma: "Cytoskelet."— Transkript prezentace:

1 Cytoskelet

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17 Tubulin jako GTP-áza

18 Samouspořádání mikrotubulárního cytoskeletu

19 Aktin a jeho polymerace

20 Stabilizace vs. destabilizace mikrotubulů, mikrotubuly vazebné proteiny

21 Aktin-vazebné proteiny

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28 ATPase Cycle “The Movie” PG-13
All myosins have a similar mechanochemical cycles ATPase Cycle “The Movie” PG-13 So how do myosins differ?

29 Myosin V transports vesicles in cells Myosin V is a “processive” motor
Myosin V HMM YFP YFP

30 Myosin V is a high (> 50%) duty ratio motor
36 nm

31 Myosin II is a low duty ratio (< 10%) motor
Myosin V -long neck (6IQ motifs) -organelle motor -functional unit: two heads Myosin II -short neck (2IQ motifs) -drives muscle contraction -functional unit: ~20 heads

32 Many myosin II molecules required to propel actin filament
In vitro motility assay Real time fluorescence microscopy

33 In muscle, myosin II molecules are assembled into a thick filament.
Filaments form by association of hydrophobic regions in the tail.

34 Muscle sarcomere is the fundamental contractile unit in muscle.
The sarcomere contracts when myosin thick filaments and actin thin filaments slide past each other.

35 Myofibril consists of a series of sarcomeres
Light and dark banding pattern gives rise to “striated” muscle. A band I band Figure Molecular Biology of the Cell

36 Sarcomere shortening (i. e
Sarcomere shortening (i.e., muscle contraction) shortens the I band but not the A band.

37 “Crowns” of crossbridges project from thick filament at 14
“Crowns” of crossbridges project from thick filament at 14.3 nm intervals and successive crowns are rotated. The result is a thick filament with six rows of crossbridges along its length.

38 Thick and thin filaments in an insect flight muscle
Thick filament Myosin Thin filament Actin

39 Accessory proteins in muscle
CapZ and tropomodulin cap ends of actin to keep filament length constant. Z disc contains -actinin and other proteins that stably join sarcomeres. Titin maintains thick filament position in the sarcomere. Nebulin sets the length of the thin filaments. Figure Molecular Biology of the Cell

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41 Levels of organization within a skeletal muscle.

42 Muscle growth Hypertrophy: Adding new myofibrils within a cell. Hyperplasia: Formation of new cells. Lengthening: Adding more sarcomeres in series.

43 Myosin mutations cause “Familial hypertrophic cardiomyopathy” and sudden death
Mouse model of hypertrophic cardiomyopathy Wt cardiac myosin R403N mutant myosin

44 Nervový vzruch vs. svalový stah

45 Mikrotubuly, kineziny dyneiny

46 Kinesiny vs. dyneiny

47 Mikrotubuly a pohyb organel a buněk

48 Kinesiny a dyneiny

49 Morfologie bičíků a řasinek

50 Ohýbání mikrotubulárních struktur

51 Srovnání kinesinu a myosinu

52 Centriola a bazální tělíska