Instant Access to the Journals You Need

for just $40 per month.

Start Your Free Trial

Roof and Floor of the Muscarinic Binding Pocket: Variations in the Binding Modes of Orthosteric Ligands

Roof and Floor of the Muscarinic Binding Pocket: Variations in the Binding Modes of Orthosteric Ligands

Abstract

Abstract Alanine substitution mutagenesis has been used to investigate residues that make up the roof and floor of the muscarinic binding pocket and regulate ligand access. We mutated the amino acids in the second extracellular loop of the M 1 muscarinic acetylcholine receptor that are homologous to the cis -retinal contact residues in rhodopsin, the disulfide-bonded Cys178 and Cys98 that anchor the loop to transmembrane helix 3, the adjoining acidic residue Asp99, and the conserved aromatic residues Phe197 and Trp378 in the transmembrane domain. The effects on ligand binding, kinetics, and receptor function suggest that the second extracellular loop does not provide primary contacts for orthosteric ligands, including acetylcholine, but that it does contribute to microdomains that are important for the conformational changes that accompany receptor activation. Kinetic studies suggest that the disulfide bond between Cys98 and Cys178 may contribute to structures that regulate the access of positively charged ligands such as N -methyl scopolamine to the binding pocket. Asp99 may act as a gatekeeper residue to this channel. In contrast, the bulkier lipophilic ligand 3-quinuclidinyl benzilate may require breathing motions of the receptor to access the binding site. Trp378 is a key residue for receptor activation as well as binding, whereas Phe197 represents the floor of the N -methyl scopolamine binding pocket but does not interact with acetylcholine or 3-quinuclidinyl benzilate. Differences between the binding modes of N -methyl scopolamine, 3-quinuclidinyl benzilate, and acetylcholine have been modeled. Although the head groups of these ligands occupy overlapping volumes within the binding site, their side chains may follow significantly different directions.
Loading next page...
 
/lp/am-soc-for-pharma-experimental-therapeutics/roof-and-floor-of-the-muscarinic-binding-pocket-variations-in-the-EwVOobFC5h

You're reading a free preview. Subscribe to read the entire article.

And millions more from thousands of peer-reviewed journals, for only $40/month.

Start Your Free Trial

What content is in DeepDyve?

  • Read and share from thousands of the leading scholarly journals from Springer, Elsevier, Nature, IEEE, Wiley-Blackwell and more.
  • All the latest content is available, no embargo periods.

Rent Scholarly Articles?

  • Read the full article in your browser.
  • Access all of your rentals from the cloud anywhere you have an internet connection.
  • Beautiful reading experience – Full charts and figures, just like the PDF.
  • Read as much as you'd like - whenever you'd like.

Happy Users

“In one word renting from DeepDyve is FANTASTIC!!! ... 99% of the time I only need access to an article for a month or so, so renting the articles is perfect for me.”

Adam S.

“Thanks for a great service! For an unaffiliated science blogger like myself this is like a dream come true.”

Seppo P.

“Hi guys, I cannot tell you how much I love this resource. Incredible. I really believe you've hit the nail on the head with this site in regards to solving the research-purchase issue.”

Daniel C.

“Let me seize this opportunity and congratulate you on the service you are rendering to the scientific community.”

Joao B.