BBMB 405 1st Edition Lecture 41 Outline of Last Lecture XVIII Chapter 33 Sensory Systems D Hearing depends on the speedy detection of mechanical stimuli E Photoreceptor molecules in the eye detect visible light XIX Chapter 35 Molecular Motors A Introduction Outline of Current Lecture XIX Chapter 35 Molecular Motors B Most Molecular Motor Proteins are members of the P loop NTPase superfamily C MyosinsMove along actin filaments D Kinesin and dynein move along microtubules Current Lecture XIX Chapter 35 Molecular Motors B Most Molecular Motor Proteins are members of the P loop NTPase superfamily 1 Cytoskeletal motor proteins utilize a track a Cytoskeletal fivers are tracks actin filaments microtubules b Myosin molecules form a thick filament at the center of actin filaments 2 Three major families of eukaryotic motor proteins a Myosin Move along actin filaments Less than 40 distinct myosins in humans Muscle contractions cell division organeller movement b Kinesin Move along microtubules Less than 40 distinct human kinesins Protein mRNa and vesicle transport chromosome segregation c Dynein These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Move along microtubules About 10 distinct dyneins in humans Motion of cilia and flagella vesicle transport transport during mitosis 3 Myosin dissection a Four fragments are generated by treatment of myosin with proteases b c S1 is the head light meromyosin is a coiled coil mero part of d Light chains wrap around alpha helix of head domain 4 Motor proteins are powered by ATP hydrolysis a P loop phosphate binding P loop NTPase aka Walker A motif b Myosin and kinesin both contain P loop NTPase domains structural similarities dispite lack of sequence similarity 5 Motor proteins are powered by ATP hydrolysis a Dynein motor domain is much larger than kinesin motor domain b Contains six AAA ATPase domains c Subfamily of the P loop NTPase d e 6 The tracks C MyosinsMove along actin filaments 1 The tracks a Actin filaments Globular G Actin b Microtubules Minus end is toward cell center and plus end is toward cell surface c Polar directionality d Dynamic assemble and disassemble based on subunit concentration and or nucleotide state e Filamentous actin F actin tropomyosin 2 Dynamics of F actin are based on critical concentration of G actin a Critical concentration CC concentration at which actin polymerizes b See figure in sides 3 ATP binding and hydrolysis is coupled to motor protein movement and track binding transition state analog for ATP hydrolysis post ATP hydrolysis and release of Pi power stroke 90 degree rotation of lever arm switch loops tightly conform to gammaphosphoryl and relax when group is absent 4 Myosin moving along actin error in figure yellow arm should be switched in drawing between steps 4 and 5 5 Kinesin and dynein a Single D Kinesin and Dynein move along microtubules 1 Kinesin and dynein are processive and travel in specific direction a Single TMR labeled dynein molecules can be seen moving processively along axonemal microtubules b 2 The relay helix and neck linker contribute to kinesin movement a Neck linker is flexible b Nucleotide exchange occurs upon association of head domain ADP complex with microtubule c Neck linker conforms along head domain increasing affinity for microtubule d Conformational change repositions other head domain e ATP is hydrolyzed upon head domain interaction with microtubule 3 Kinesin moving along microtubule processive hand over hand movement
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