Cytoskelet

Tubulin jako GTP-áza

Samouspořádání mikrotubulárního cytoskeletu

Aktin a jeho polymerace

Stabilizace vs. destabilizace mikrotubulů, mikrotubuly vazebné proteiny

Aktin-vazebné proteiny

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

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

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

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

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

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

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

Myofibril consists of a series of sarcomeres Light and dark banding pattern gives rise to “striated” muscle. A band I band Figure 16-69 Molecular Biology of the Cell

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

“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.

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

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 16-72 Molecular Biology of the Cell

Levels of organization within a skeletal muscle.

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

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

Nervový vzruch vs. svalový stah

Mikrotubuly, kineziny dyneiny

Kinesiny vs. dyneiny

Mikrotubuly a pohyb organel a buněk

Kinesiny a dyneiny

Morfologie bičíků a řasinek

Ohýbání mikrotubulárních struktur

Srovnání kinesinu a myosinu

Centriola a bazální tělíska