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Lectures 12 - 14 - Membranes

Bacteriorhodopsin bacteriorhodopsin bacteriorhodopsin

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Unformatted text preview: Bacteriorhodopsin Bacteriorhodopsin Bacteriorhodopsin exists in 2 states : Tense (T) – binds trans-retinal Relaxed (R) – binds cis-retinal T state: Schiff Base is protonated Excitation by photon Isomerization H + transferred from Schiff base to Asp 85 R state: H + transferred from Asp 96 to Schiff base and H + from Asp 85 is transferred to Extracellular Space H + transferred from Cytoplasm to Asp 96 Photosiomerization of retinal Bacteriorhodopsin photocycle Bacteriorhodopsin photocycle Bacteriorhodopsin photocycle Porin • Homotrimeric protein. – Each monomer is made of a 16 stranded Up/Down β Barrel. – Subunits interact by polar loop and hydrophobic side chain interactions. • Periplasmic End: short and smooth Cytoplasmic End: funnel shaped, made of long loops with hydrophilic residues. • Eyelet = loop connecting β 5 and β 6 extending into the central open cavity of the barrel. – Cavity is lined with charged residues, arranged in an electrochemical gradient. Fig12.7 Porin Trimer Porin – Aromatic Belt Aromatic Belt – mainly Phe and Tyr • Has polar and hydrophobic character to interactive with the hydrophilic space of the membrane extracellular solution and hydrophobic internal space of the membrane....
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Bacteriorhodopsin Bacteriorhodopsin Bacteriorhodopsin...

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