Lecture 16.5 11/16/07 Clarifications of Actin and Filaments/Critical ConcentrationActin and filaments•2 main forms:oFree actin = monomersoG-Actin = globular (in book)oFree monomers come together F-actin, or filamentous actin•Actins – monomers and filaments have polarityo(+) (-)end polarityoBarbed (+) vs. Pointed (-) how filament looks like under microscopeoATP at (+) end, more likely to stick to each otheroADP at (-) end, less likely to stick to each otheroAddition of monomers at (+) end has a higher affinity for acquiring monomers in ATP form, bind more tightly to each other. After monomers incorporate into filament, ATP ADP hydrolysis, which makes filament more likely to depolymerize, considering state of ADP monomers less likely to stick to each other. oATP cap causes a higher affinity, keeps filament from falling apart, after the hydrolyze to ADP depolymerizationCritical Concentration•Treadmilling – net loss of monomers from (-) end and net gain of monomers to (+) endo
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