Biology 2382B Lecture Notes - Proline, A Band, Actomyosin Ring
Document Summary
Mitotic spindle flagella/cilia components of axons: made of 13 longitudinal repeating units called protofilaments, brain microtubules were purified to find a protein called tubulin, which is a microtubule. Microtubule walls are polarized structures built from - tubulin. Purified soluble tubulin is a dimer made of two closely related subunits; and tubulin of 55000. Daltons each (there is also -tubulin, which is used in regulatory function) Each subunit of the tubulin dimer can bind one molecule of gtp. Gtp trapped in the -tubulin is never hydrolyzed. Gtp in the -tubulin is exchangeable with the free gtp, and can be hydrolyzed. Mt consist of 13 laterally associated protofilaments forming a tube whose external diameter is 25nm. Each protofilaments is made up of alternating -tubulin dimers, with each subunit type repeating each. Each protofilaments has an alpha at one end and a beta at the other end, giving the protofilaments an intrinsic polarity.
