The structure of MreB protein resembles that of the eukaryotic protein actin, which polymerizes to form cytoskeletal filaments in eukaryotic cells.

TLS Online TPP Program

#Id: 9304

#Unit 4. Cell Communication and Cell Signaling

In the absence of light,  bound 11-cis-retinal locks the rhodopsin into its inactive (R) conformation

TLS Online TPP Program

#Id: 9305

#Unit 4. Cell Communication and Cell Signaling

Absorption of light causes rapid photoisomerization of the bound cis-retinal to the all-trans isomer, triggering a conformational change in opsin that activate the Gαt.

TLS Online TPP Program

#Id: 9306

#Unit 4. Cell Communication and Cell Signaling

There are about 90 million rod cells in the human retina, and each contains about 4x107 molecules of rhodopsin that are very densely packed in the membrane disks.

TLS Online TPP Program

#Id: 9307

#Unit 4. Cell Communication and Cell Signaling

A single activated rhodopsin protein activates 

~13 transducin molecules in the few seconds before the covalent bond between the opsin protein and all-trans-retinal is spontaneously cleaved

TLS Online TPP Program

#Id: 9308

#Unit 4. Cell Communication and Cell Signaling

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: 9309

#Unit 4. Cell Communication and Cell Signaling

Autosomal recessive mutations in the RPE65 gene are a frequent cause of blindness in children.