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Journal Article

Restricted Diffusion of Tyrosine Hydroxylase and Phenylethanolamine N-methyltransferase from Digitonin-Permeabilized Adrenal Chromaffin Cells

Katrina L. Kelner, Kyoji Morita, Jonathan S. Rossen and Harvey B. Pollard
Proceedings of the National Academy of Sciences of the United States of America
Vol. 83, No. 9 (May 1, 1986), pp. 2998-3002
Stable URL: http://www.jstor.org/stable/26962
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Restricted Diffusion of Tyrosine Hydroxylase and Phenylethanolamine N-methyltransferase from Digitonin-Permeabilized Adrenal Chromaffin Cells
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Abstract

Tyrosine hydroxylase [TyrOHase; tyrosine 3-monooxygenase; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2] and phenylethanolamine N-methyltransferase (PMTase; S-adenosyl-L-methionine:phenylethanolamine N-methyltransferase, EC 2.1.1.28) are involved in catecholamine biosynthesis and are considered soluble proteins. However, they may actually be localized on the surface of the chromaffin granule. We have used the detergent digitonin to permeabilize the plasma membrane of cultured adrenal chromaffin cells to investigate the subcellular localization of TyrOHase and PMTase. A digitonin titration of the release of proteins and catecholamines revealed the existence of at least three subcellular compartments that are distinguished by their digitonin sensitivity: (i) soluble proteins, which were released upon treatment of the cells with low digitonin concentrations (5 μ M), (ii) a ``digitonin-sensitive'' cytoplasmic protein pool, which required higher concentrations of digitonin for release (10 μ M) and included TyrOHase and PMTase, and (iii) the chromaffin granule, which was insensitive to digitonin. Analysis of the rates of release of all of these proteins revealed that the rate of TyrOHase and PMTase release was slower at 10 μ M than at 40 μ M digitonin, while the rates of release of the other proteins were similar at both concentrations and varied in proportion to their respective sizes. Treatment with cytoskeletal disrupting agents had no effect on TyrOHase or PMTase efflux. These data suggest that TyrOHase and PMTase are in a detergent-labile association in the cell. This is consistent with the concept that TyrOHase and PMTase may be localized on the surface of the chromaffin granule.

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