GPCRs

The G protein-coupled receptor (GPCR) superfamily has more than 800 members in the human genome, detecting a variety of extracellular chemical, biological, or physical signals that are critical for human biology and disease. Understanding their three-dimensional (3D) structures will help understanding their function and will enable the development of new therapeutic molecules. 

 Ion channels are pores that open and close in an all-or-nothing fashion on time scales of 0.1 to 10 ms to provide aqueous channels through the plasma mem­brane that ions can traverse. There are a number of drugs which act by modulat­ing the ion channels.

Ion channels that are normally modulated by membrane potential are known as voltage-sensitive ion channels. Voltage-sensitive ion channels mediate the conductance of sodium, calcium, and potassium. They provide rapid changes in ion permeability. These channels exhibit high ion selectivity, voltage sensitivities, and single-channel conductance.

ATP-binding cassette transporters (ABC-transporters) catalyze the vectorial transport of a great variety of substrates across biological membranes. They are intricate molecular systems that have representatives in all extant phyla from prokaryotes to humans. They are one of the largest and ancient protein superfamilies and are able topower the translocation of substrates (including sugars, amino acids, metal ions, peptides/proteins, and a large number of hydrophobic compounds) across biological membranes, often against a concentration gradient, by the hydrolysis of ATP.

Solute carriers (SLC) are a group of membrane transport proteins, comprising over 400 members, most of which are located incell membranes. Their main function is to facilitate the transport of a wide variety of substrates across biological membranes, including the uptake of small molecules into cells.