Molecular Pharmacology, Vol 2, 298-310, Copyright © 1966 by the American Society for Pharmacology and Experimental Therapeutics

Some Chemical and Physical Properties of the Soluble Protein Fraction of Bovine Adrenal Chromaffin Granules

¹ Department of Pharmacology, University of Oxford, England

1. The soluble protein fraction, 70% of the total protein of the chromaffin granules of the bovine adrenal medulla, has been prepared by ethanol precipitation. The protein fraction was freed of nucleotides by gel filtration, and its sedimentation properties and amino acid composition have been studied.

2. The sedimentation pattern showed a single peak with a slight asymmetry which is interpreted as indicative of a molecular heterogeneous system. A sedimentation constant of s⁰_20,w = 2.0 and an average apparent molecular weight of 25,000 was calculated for this peak.

3. The soluble protein fraction was very rich in glutamyl (or glutaminyl) residues (25.4% by weight), and its proline content was high. No cysteine was found. The negatively charged groups were found to outnumber the positively charged groups by 7 residues per protein molecule.

4. This peak was further fractionated into two subfractions which had identical electrophoretic mobility patterns but differed in their sedimentation properties.

5. It is suggested that the soluble protein interacts with low molecular weight ions, leading to physically distinguishable molecular forms of the same protein unit.

Note:
ACKNOWLEDGMENTS This research has been supported by a grant from the University of Bergen and by grants to Dr. H. Blaschko from time U.S. Air Force, European Office of Aerospace Research and from the U.S. Public Health Service, National Institute of Neurological Diseases and Blindness (for the Farrand spectrofluorometer used in this work). The author wishes to thank Dr. H. Blaschko, F.R.S., for hospitality during the academic year of 1962-1963 and for continuous encouragement and help. The author is indebted to Dr. W. E. van Heyningen for help and advice in the use of his analytical ultracentrifuge, to Dr. D. E. Hope for the amino acid analysis, to Dr. P. Banks for advice and help given in prepatation of chromaffin granules, to Dr. E. J. Schuster for the design of the centrifuge tube cutter used in this work, and to Mrs. Helen Thomas for skillful technical assistance.

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