Investigations of the Structural Properties of the Acetylcholine Receptor and its Polypeptide Subunits from Torpedo Californica

Author: Strader, Catherine Boxley Devine

Year: 1980

Degree: Dissertation (Ph.D.)

Advisor: Raftery, Michael A.

Committee Member: Unknown, Unknown

Option: Chemistry

DOI: 10.7907/n480-zm70

Abstract

Microsequence analysis of the four polypeptide subunits of the acetylcholine receptor from Torpedo californica electroplax was performed and demonstrated a striking amino acid homology among these four chains. Further sequence analysis of both membrane-bound and Tritonsolubilized, chromatographically purified receptor was used to measure the stoichiometry of the subunits. The values determined for the two preparations of receptor were the same: the ratio of the four subunits (40,000: 50,000:60,000:65,000 daltons) is 2:1:1:1, indicating a value of255,000 daltons for the molecular weight of the receptor, in agreement with experimentally determined values. These results demonstrate that the acetylcholine receptor is a pentamer composed of five subunits, two being identical and the other three being structurally related to them by sequence homology. Genealogical analysis suggests that divergence from a common ancestral gene occurred early in the evolution of the receptor. This shared ancestry argues compellingly that each of the four subunits plays a functional role in the receptor's physiological action.

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