Protein Structure and Function

GPCR Structure and Function

• The β2 adrenergic receptor shows an active vs inactive state, G-protein activation, and β-arrestin activation.
• The receptor has a conserved seven-pass transmembrane fold, with a covalently attached palmitate linked to an eighth helix.
• The bound ligand carazolol is shown as yellow spheres behind TM6 and TM7.

Class B Family GPCRs

• Several structures were reported in 2017, including the Calcitonin Receptor and GLP-1 Receptor.

Fatty Acid Receptor GPCR

• The GPR120 receptor was reported in 2023.

Rhodopsin (Bacteriorhodopsin)

• Rhodopsin is a 26 kDa protein containing the pigment retinal and functions as a light-driven proton pump in photosynthesis.
• The protein occurs naturally as a 2-D crystal about 1 μm in diameter and 45 Å thick.

Integral Membrane Proteins

• Hydrophobicity plots can be used to locate TM segments.
• TMHMM can predict TM segments.
• The positive inside rule can predict the topology of TM segments.

Channel Proteins and Transporters

• Channel proteins and transporters are types of integral membrane proteins.

GPCR Signaling

• GPCRs can signal through G-protein or arrestin pathways.
• GRKs (G-protein-coupled receptor kinases) play a role in GPCR signaling.

Aquaporin

• Aquaporin is a channel protein that allows glycerol to pass through the membrane.
• The protein has a quasi twofold symmetry, with a channel pathway lined with glycerol molecules.
• Molecular dynamics simulations have been used to understand aquaporin specificity.
• Aquaporin selectivity is controlled by global orientational tuning.
• The NPA motif is highly conserved in aquaporin repeats.
• Aquaporin prevents proton conduction.

Potassium Channels

• Potassium channels are one of the most common channel types in nature.
• The KcsA channel is a simple bacterial potassium channel with a selectivity filter.