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e. Look at the sequence of the human GABA-receptor (83 subtype) - a ligand gated

ID: 3165840 • Letter: E

Question

e. Look at the sequence of the human GABA-receptor (83 subtype) - a ligand gated Ch channel-as found at https://www.rcsb.org/pdb/explore/remediatedSequence.do?structureld 4COF and identify the following (providing both the one letter code and residue # for any particular residue meeting the indicated criterion, 2 points. each) (A) A residue predicted to bind (or have attached to it) a polysaccharide (B) A positively charged (at physiological pi?l) residue (eg one that can favorably interact with Cl ions) within a transmembrane helix (C) A tryptophan or tyrosine at the C-terminal end of a transmembrane helix A residue in an extra-cellular part of the receptor (hint: what happens to cysteine residues co-located in space, even if apart in sequence, in an oxidizing environment?) (D)

Explanation / Answer

A) From the sequence, we get that Glutamine at 26th position is responsible for binding of ligands.

B) The arginine at 216 is present in the transmembrane helix.

C) The tyrosine residue is present at 299 position.

D) Two cysteine residues make salt bridges that enable the stabilization of the extracellular part of the receptor.