Dual hairpin formation (Region 3-4 forms hairpin then second hairpin is formed between Region 1-2) release RNA-DNA hybrid and RNA Polymerase causes seizing transcription of trp operon at high trp concentration.

#Id: 1505

#Unit 2. Cellular Organization

The tubulin subunit is a heterodimer formed from two closely related globular proteins called a-tubulin and b-tubulin.

#Id: 1506

#Unit 2. Cellular Organization

a-tubulin and b-tubulin comprising 445–450 amino acids, which are tightly held together by noncovalent bonds.

#Id: 1507

#Unit 2. Cellular Organization

Each α or β monomer has a binding site for one molecule of GTP.

#Id: 1508

#Unit 2. Cellular Organization

The GTP that is bound to α-tubulin is physically trapped at the dimer interface and is never hydrolyzed.

#Id: 1509

#Unit 2. Cellular Organization

GTP-binding site on the β-subunit is at the surface of the dimer and GTP bound by the β-subunit can be hydrolyzed.

#Id: 1510

#Unit 2. Cellular Organization

A microtubule is a hollow cylindrical structure built from 13 parallel protofilaments, each composed of αβ-tubulin heterodimers stacked head to tail and folded into a tube.