HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 276, Issue 26, 23589-23598, June 29, 2001

This Article Full Text Full Text (PDF) All Versions of this Article: 276/26/23589    most recent M102350200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Papineni, R. V. L. Articles by Pedersen, S. E. Search for Related Content PubMed PubMed Citation Articles by Papineni, R. V. L. Articles by Pedersen, S. E. Social Bookmarking                      What's this?

Site-specific Charge Interactions of -Conotoxin MI with the Nicotinic Acetylcholine Receptor^*

Rao V. L. Papineni, Jovanny Ulloa Sanchez^§, Krishna Baksi^§, Irmgard Ursula Willcockson^¶, and Steen E. Pedersen

From the  Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030 and the ^§ Department of Anatomy and Cell Biology, Universidad Central del Caribe, Bayamon, Puerto Rico 00960-6032

We have tested the importance of charge interactions for -conotoxin MI binding to the nicotinic acetylcholine receptor (AChR). Ionic residues on -conotoxin MI were altered by site-directed mutagenesis or by chemical modification. In physiological buffer, removal of charges at the N terminus, His-5, and Lys-10 had small (2-4-fold) effects on binding affinity to the mouse muscle AChR and the Torpedo AChR. It was also demonstrated that conotoxin had no effect on the conformational equilibrium of either receptor, as assessed by the effects of the noncompetitive antagonist proadifen on conotoxin binding and, conversely, the effect of conotoxin on the affinity of phencyclidine, proadifen, and ethidium. Conotoxin displayed higher binding affinity in low ionic strength buffer; neutralization of Lys-10 and the N terminus by acetylation blocked this affinity shift at the site but not at the site. It is concluded that Ctx residues Lys-10 and the N terminal interact with oppositely charged receptor residues only at the site, and the two sites have distinct arrangements of charged residues. Ethidium fluorescence experiments demonstrated that conotoxin is formally competitive with a small cholinergic ligand, tetramethylammonium. Thus, -conotoxin MI appears to interact with the portion of the binding site responsible for stabilizing agonist cations but does not do so with a cationic residue and is, consequently, incapable of inducing a conformational change.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				I. U. Willcockson, A. Hong, R. P. Whisenant, J. B. Edwards, H. Wang, H. K. Sarkar, and S. E. Pedersen Orientation of d-Tubocurarine in the Muscle Nicotinic Acetylcholine Receptor-binding Site J. Biol. Chem., October 25, 2002; 277(44): 42249 - 42258. [Abstract] [Full Text] [PDF]