RPE65 is the enzyme in the pigment epithelial cells of the retina that catalyzes the isomerization of the intermediate esterified all-trans retinol to 11-cis-retinol.

TLS Online TPP Program

#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.

TLS Online TPP Program

#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.

TLS Online TPP Program

#Id: 1511

#Unit 2. Cellular Organization

Tubulin dimers in which the β-subunit has bound GTP are added preferentially to (+) end of the microtubule.

TLS Online TPP Program

#Id: 1512

#Unit 2. Cellular Organization

In a microtubule,

The end with exposed β-subunits is the (+) end

The end with exposed α-subunits is the (−) end

 

TLS Online TPP Program

#Id: 1513

#Unit 2. Cellular Organization

Microtubules exist in three forms:

Singlet

Doublet

Triplet

TLS Online TPP Program

#Id: 1514

#Unit 2. Cellular Organization

Most microtubules in a cell consist of a simple tube, a singlet microtubule, built from 13 protofilaments.