Final Exam Pt 4
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| Many molecular motors are members of the _____ family | P-loop NTPase
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| The first kinesin discovered was called _____ | conventional kinesin
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| In kinesin, a _____ undergoes conformational change after nucleotide binding | neck linker
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| The functional unit in a muscle cell is a | sarcomere
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| _____ is the name given to actin monomers | G-actin
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| _____ is a prokaryotic homolog of actin | MreB
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| An ____ is a bundle of nine microtubule pairs surrounding two singlet microtubules. | axoneme
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| A prokaryotic protein similar to tubulin is called a ____ | FtsZ
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| Flagella are used for ____ in bacteria. | chemotaxis
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| Molecules such as glucose that attract bacteria are termed ____ | Chemoatractants
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| Myosin light chains are related to the ____ family of proteins. | EF hand
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| A helical section that moves dramatically when NTP is bound is called the ____ in P-loop NTPases. | lever arm
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| Troponin reacts in response to the ion ____ | calcium
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| During a muscle contraction, the thin filaments (actin, tropomyosin, troponin) slide along the ______ | thick filaments
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| Single molecules of myosin in actions were studied using ____ | an optical trap
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| Actin likely evolved from a protein that bound ______ | ATP
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| Microtulules are tracks for kinesins and _____ | dyneins
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| Taxol inhibits the proliferation of cells by stabilizing the polymer form of ____ | microtubules
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| Bacterial flagella are polymers composed of 53-kd subunits of a protein called _____ | flagellin
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| Bacterial flagella rotate in one direction for smooth swimming and in the other direction to cause ____ | tumbling
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| Energy used to propel molecular motors includes | ATP, ion gradients
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| The major family(ies) of eukaryotic motor proteins is(are) | myosins, kinesins, dyneins
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| The structure of dynein lends itself to the formation of | oligomers
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| Binding of ATP causes ____ in myosin head affinity for actin filaments | a decrease
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| Binding of ATP causes _____ in kinesin affinity for microtubules. | an increase
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| Actin polymers will assemble | automatically by self-assembly
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| How is MreB similar to actin? | It folds into a similar tertiary structure, and Like F actin, it forms polymers.
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| What is the rate and distance of the movement of myosin heads? | Each head moves 5 times per second, approximately 110 Angstroms
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| How does the length of the lever arm affect the rate? | A mutated shorter arm has a reduced rate, and a mutated longer arm has a faster rate
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| Human spastic paraplegia has been linked to a mutation in | kinesin family genes
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| Bacterial motors differe from eukaryotic ones in that the bacterial motor | spins around a central axis
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| What is the energy source used to rotate the flagella? | proton gradient
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| The structure in bacteria that rotates is referred to as | the MS ring
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| The biased random walk motion of bacteria is the result of | swimming with more tumbling when moving away from a chemorepellant
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| Molecules that cause bacteria to swim away from toxic substances are | chemorepellants
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| How do molecular motors work? | Proteins undergo conformational changes, in very small increments, which are converted to motor type activity
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| To what families are myosin, kinesin, and dynein related (in humans)? | While amino acid sequences are varied, the 3-dimensional structures of myosin & kinesin are similar to the P-loop NTPase domains that r observed in G proteins. Dynein contains domains structurally similar to the P-loop NTPase domains in the AAA subfamily
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| Briefly describe the structure of myosin | Myosin consists of a long stalk-like region with two heads at one end. The ATP-binding domains are near the heads, and the long stalk serves as an attachment site to other proteins
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| What serves as the track for myosin? | Actin, in a polymeric form, serves as the molecular track for myosin
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| What is F-actin? | The filamentous form of actin is a helical structure formed from actin monomers. It resembles a two-stranded string or cable. One end contains a "point" and the other end is "barbed"
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| What was learned using the optical trap laser studies? | The Studies indicated myosin heads undergo structural changes in conformation when they bind to actin that pulls the actin filament, leading to a displacement of the beads.After a time period, the actin is released& rturns to orig position between 2 beads
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| Describe the experiment that supports role of the lever arm in myosin motor activity | Investigators deleted sequences to shorten the lever arm & inserted sequences to extend the lever arm. The rate of myosin movement along an active filament decreased as the lever arm was shortened & increased as the lever arm was extended
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| What is the cause of Charcot-Marie-tooth disease? | This neuropathy is caused by a mutation in kinesin type K1F1B~B
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| How does the action of kinesin differ from that of myosin on its track? | Myosin binds and releases actin after each stroke. In contrast, kinesin is a processive enzyme. The heads operate in concert, with one, then the other binding.
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| Compare the speed of movement of a motile bacterium to a human | the bacterium can move approximately 25 um/sec or about 10 body lengths. To achieve this a human would have to run a 100-m dash in 5 sec.
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| How is a bacterial motor similar to ATP synthase? | In both cases, a proton moving across a membrane into a channel causes a structure to rotate.
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| How are flagellin subunits arranged in the bacterial flagellum? | Flagellin subunits form helical polymers containing 5.5 subunits/turn. The subunits are arranged around a hollow core and can extend up to 15 um in length
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| Is the motion of a bacteria deliberate and exact toward a target chemoattractant, or is it random? | While the bacteria will eventually arrive at its source, there is a great deal of random movement caused by the tumbling as it seeks the proper direction
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