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39 Cards in this Set
- Front
- Back
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Mechanochemical cycle of molecular motors
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filament binding, conformational change, filament release
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What are molecular motors used for?
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diverse processes from muscle contraction to vesicle movement;
convert chemical energy of ATP hydrolysis to mechanical motion |
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Types of molecular motors
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actin based motors
microtubule based motors - kinesin and kinesin-like proteins (+end directed) - dyneins (- end directed) |
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Myosin II
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aka. muscle myosin
motor 2 (>200kDa) heavy chains and 2 light chains heavy chains have globular heads w/ ATPase activity heavy chain tails form coiled-coil of two a-helices |
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Coiled coils:
examples of 2, 3, and 4 stranded? what dictates its structure? |
interaction of 2 or more alpha helices
2 stranded: myosin II, intermediate filaments, tropomyosin 3-stranded: viral fusion proteins like hemagglutinin 4-stranded: formed by SNARE proteins structure dictated by amino acid side chain arrangement. hydrophobic positioned in 1st and 4th position of a 7aa repeat. |
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Skeletal muscle sarcomere
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thick filament (myosin)
thin filament (actin) |
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Myosin + trypsin
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light meromyosin + heavy meromyosin
(neck region is sensitive to serine protease trypsin) |
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myosin + trypsin + papain
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light meromyosin
+ heavy meromyosin split by papain into: S2 + S1 + S1 |
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What are the two types of myosin light chains and what do they do?
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"essential light chain" binds Ca2+
"regulatory light chain" binds Mg2+ these small proteins show similarity to calmodulin, which binds Ca2+ |
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kinesin and kinesin-related proteins
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"+ end" directed microtubule motors
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Actin-myosin crossbridge cycle
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1. rigor state: tight binding of myosin and actin
2. ATP binds to myosin, myosin dissociates 3. Myosin hydrolyzes ATP 4. Relaxed state; myosin head swings and binds weakly to a new actin molecule 5. Power stroke; initated by the release of Pi |
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Kinesin mechanochemical cycle
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When ATP binds to the leading head, conformational changes in the linker region drive movements of the trailing head.
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Kinesin vs. myosin
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both move towards + end
kinesin: - moves towards + end of MICROTUBULE - binds tightly to microtubules WITH bound ATP myosin: - moves towards + end of ACTIN - binds tightly to actin withOUT nucleotide (rigor state) |
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Dynein moves vesicles towards _________ of _________.
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the minus end of microtubules
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Kinesin moves vesicles towards the __________ of ________.
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the plus end of microtubules
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Myosin II vs. Myosin V
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Myosin II has a 5-10nm swing of lever arm; Myosin V has 30-40nm swing.
the modification of the level arm affects the rate of transport vesicle movement. |
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Golgi perinuclear localization depends on ______
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microtubules
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What are the different components of the mitotic spindle?
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microtubules:
1. astral 2. kintochore 3. interpolar kinetochores connecting the sister chromatids to the kinetochore microtubules 2 pairs of centrosomes motor proteins |
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Name the actin-based structures used for movement
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1. filopodia
2. lamellipodia 3. pseudopodia |
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Filopodia
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one of three types of actin-based structures used for movement
-1D finger-like projection -similar to microvilli, but more dynamic - core of long, bundled actin filaments |
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Lamellipodia
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one of three types of actin-based structures used for movement
- 2D sheet-like structure - cross-linked mesh of actin filaments |
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Pseudopodia
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one of three types of actin-based structures used for movement
- short 3D projections - used by neutrophils and macrophages for phagocytosis - actin filament gel |
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Examples of downstream signals from Rac that mediate actin filament changes
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Leads to brached actin web in lamellipodia:
- ARP (branching nucleator) - Filamin (web crosslinker) Leads to less stress and fiber formation - decreased myosin activity |
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Cytoplasmic dynein
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2 heads + 2 light chains
organelle movement MT movement during cell cycle |
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Axonemal/ciliary dyneins
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3 heads + lots of light chains
the fastest motor proteins can move 14um/s compared to 2-3um/s for kinesin and 2-5um/s for myosin II |
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Structure of myosin and kinesin heads
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no primary sequence similarity, BUT similar 3D fold
suggests that mechanism of translating chemical energy into mechanical energy is the same |
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Cytoplasmic dynein
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2 heads + 2 light chains
organelle movement MT movement during cell cycle |
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Axonemal/ciliary dyneins
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3 heads + lots of light chains
the fastest motor proteins can move 14um/s compared to 2-3um/s for kinesin and 2-5um/s for myosin II |
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Cytoplasmic dynein
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2 heads + 2 light chains
organelle movement MT movement during cell cycle |
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Structure of myosin and kinesin heads
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no primary sequence similarity, BUT similar 3D fold
suggests that mechanism of translating chemical energy into mechanical energy is the same |
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Cytoplasmic dynein
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2 heads + 2 light chains
organelle movement MT movement during cell cycle |
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Axonemal/ciliary dynein
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3 heads + lots of light chains
the fastest motor proteins can move 14um/s compared to 2-3um/s for kinesin and 2-5um/s for myosin II |
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Structure of myosin and kinesin heads
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no primary sequence similarity, BUT similar 3D fold
suggests that mechanism of translating chemical energy into mechanical energy is the same |
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Axonemal/ciliary dynein
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3 heads + lots of light chains
the fastest motor proteins can move 14um/s compared to 2-3um/s for kinesin and 2-5um/s for myosin II |
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Structure of myosin and kinesin heads
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no primary sequence similarity, BUT similar 3D fold
suggests that mechanism of translating chemical energy into mechanical energy is the same |
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Dynein's method of attachment of motor protein to vesicle
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uses a short piece of actin bound to the surface of a vesicle through other actin binding proteins like Arp1, psectrin, and the dynactin complex
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Myosin V's method of attachment of motor protein to vesicle
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use actin filaments and myosins
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Dynein's method of attachment of motor protein to vesicle
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uses a short piece of actin bound to the surface of a vesicle through other actin binding proteins like Arp1, psectrin, and the dynactin complex
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Myosin V's method of attachment of motor protein to vesicle
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use actin filaments and myosins
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