Faculty Research 1970 - 1979

Title

Kinetics of biosynthesis of acetylcholine receptor and subsequent incorporation into plasma membrane of cultured chick skeletal muscle.

Document Type

Article

Publication Date

1977

Keywords

Bungarotoxins, Cell-Membrane: me, Cells-Cultured, Kinetics, Receptors-Cholinergic: de, bi, me, SUPPORT-U-S-GOVT-P-H-S

JAX Source

Cell. 1977 Mar; 10(3):365-73.

Abstract

20% of the acetylcholine receptors in cultured chick skeletal muscle remain unbound following long-term growth of muscle in medium containing a potent, essentially irreversible receptor-blocking agent, alpha-bungarotoxin. About half the receptors which are unavailable for interaction with extracellular alpha-bungarotoxin are newly synthesized molecules which presumably are being processed and transported to the plasma membrane. When the muscle cultures are switched to a medium containing 2H, 13C, 15N-amino acids, these receptors are rapidly labeled, the fraction of labeled molecules beginning to plateau at 3 hr. Few labeled receptors appear in the plasma membrane during the first 3 hr of labeling with 2H, 13C, 15N-amino acids. After 3.5 hr of labeling, virtually all the receptors being incorporated into the plasma membrane are labeled receptors. The kinetics of labeling of the "pool: and "surface: receptors with 2H, 13C, 15N-amino acids confirm the "precursor-product: type relationship of pool and surface acetylcholine receptors. In this study, receptors synthesized in medium containing 2H, 13C, 15N-amino acids were resolved from 1H, 12C, 14N-receptors by velocity sedimentation in sucrose-deuterium oxide and sucrose-H2O gradients, and their densities were estimated from sedimentation rates in shallow gradients of various average density. Estimated densities were 1.32 g/cm3 for 1H, 12C, 14N-receptors and 1.41 g/cm3 for 2H, 13C, 15N-receptors. This density difference corresponds to 80% substitution of normal aminoacyl residues by 2H, 13C, 15N-residues in the denser receptor.

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