Biology 2382B Lecture Notes - Lecture 5: Atp Hydrolysis, Depolymerization, Dynactin

• School: Western University
• Department: Biology
• Course: Biology 2382B
• Professor: Sashko Damjanovski

Document Summary

A(cid:374)d -tubulin forms a dimer -tubulin dimer is the basic subunit. The dimer is very stable; does not disassemble once formed. -tubulin can hydrolyze its gtp; can be either gtp or gdp bound. Di(cid:373)e(cid:396)s a(cid:396)e li(cid:374)ed i(cid:374) a (cid:396)epeated (cid:373)a(cid:374)(cid:374)e(cid:396) to (cid:373)ake protofilaments. As the p(cid:396)otofila(cid:373)e(cid:374)t g(cid:396)o(cid:449)s, the -tu(cid:271)uli(cid:374)(cid:859)s gtp is h(cid:455)d(cid:396)ol(cid:455)zed. Since dimers are polar, the complete microtubule is also polar. Pol(cid:455)(cid:373)e(cid:396)ized (cid:373)i(cid:272)(cid:396)otu(cid:271)ules appea(cid:396) as hollo(cid:449) tu(cid:271)es (cid:894)(cid:1006)(cid:1009)(cid:374)(cid:373) dia(cid:373)ete(cid:396); ~(cid:1005)(cid:1004)(cid:1004) (cid:373) lo(cid:374)g(cid:895) Cells a(cid:396)e ~(cid:1005)(cid:1004) (cid:373) the microtubules stick out (flagella, antennae, etc. ) The protofilaments arrange in a ring to form the hollow microtubule (mt) structure. The singlet is the most common form the 13 protofilament ring forms a 25nm wide mt. the doublets and triplets are also stable. To extend a singlet form more rings, another 10 protofilaments are added each time. In the multi-(cid:396)i(cid:374)ged mts, ea(cid:272)h (cid:396)i(cid:374)g is la(cid:271)elled as a, b, c, a(cid:374)d so o(cid:374) . Two types of microtubules: cytoplasmic and axonemal (cilla, flagella etc. )