BIOLOGY 2B03 Lecture Notes - Lecture 17: Depolymerization, Ford Power Stroke Engine, Immunoglobulin Light Chain
Document Summary
Tube made of 13 protofilaments arrayed in a staggered (means it appears to spiral up like a spring) circular pattern to form strong wall. Subunits di(cid:373)ers of a(cid:374)d -tubulin units. Whe(cid:374) a(cid:374)d protei(cid:374)s (cid:271)i(cid:374)d together, the(cid:455) for(cid:373) the monomer - -heterodimer. -tubulin: always bound to gtp and does not hydrolyze and does not exchange nucleotides. -tubulin: cyclically bound to gtp and gdp after hydrolysis. - -gtp binds with much higher affinity to the growing (cid:373)i(cid:272)rotu(cid:271)ule fila(cid:373)e(cid:374)t tha(cid:374) does - -gdp. Microtubules are polar filaments like actin filaments. (+) end fast growing (-) end slow growing. The - -di(cid:373)er orie(cid:374)ts the -subunit closer to the (+) end (cid:449)hile the -subunit is closer to the (-) end. Di(cid:373)ers of - -gtp are added to the (+) end of growing filament = rescue (cid:449)hile the - -gdp are released = catastrophe. Once attached to the microtubule, gtp h(cid:455)drol(cid:455)sis o(cid:272)(cid:272)urs so the (cid:373)ajorit(cid:455) of (cid:373)o(cid:374)o(cid:373)ers are - -gdp.
