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Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types: Induction of Transformation by a Desoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III. January 1944.

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Title:	Studies on the Chemical Nature of the Substance [14 of 23]
Alternative Title:	Induction of Transformation by a Desoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III
Creator:	Avery, Oswald T.
Contributor:	MacLeod, Colin M.
Publisher:	Journal of Experimental Medicine
Date:	1944-01-00
Subject:	Cellular signal transduction
Description:	From the Journal of Experimental Medicine Vol. 79, No. 1.
Type:	Text
Format:	text/plain
Language:	en
Identifier:	avery-pg14.jpg
Source:	Master scanned with Epson GT-10000+ flatbed scanner at 600 dpi.
Rights:	http://osulibrary.orst.edu/specialcollections/coll/pauling/dna/copyright.html
Full Text:	150­RANSFORMATION OF PNEUMOCOCCAL TYPES in both instances the enzymes concerned are inactivated at the same tempera- ture and inhibited by fluoride provide additional evidence for the belief that the active principle is a nucleic acid of the desoxvribose type. Serological Analysis.-In the course of chemical isolation of the active material it was found that as crude extracts were purified, their serological activity in Type III antiserum progressively decreased without corresponding loss in biological activity. Solutions of the highly purified substance itself gave only faint trace reactions in precipitin tests with high titer Type III antipneumococcus rabbit serum." It is well known that pneumococcal protein can be detected by serological methods in dilutions as high as 1: 50,000 and the capsular as well as the somatic polysaccharide in dilutions of at least 1: 5,000,000. In view of these facts, the loss of serological reactivity indicates that these cell constituents have been almost completely removed from the final preparations. The fact that the transforming substance in purified state exhibits little or no serological reactivity is in striking contrast to its biological specificity in inducing pneumococcal transformation. Physicochenzical Studies.5-A purified and active preparation of the trans- forming substance (preparation 44) was examined in the analytical ultra- centrigue. The material gave a single and unusually sharp boundary indicating that the substance was homogeneous and that the molecules were uniform in size and very asymmetric. Biological activity was found to be sedimented at the same rate as the optically observed boundary, showing that activity could not be due to the presence of an entity much different in size. The molecular weight cannot be accurately determined until meas- urements of the diffusion constant and partial specific volume have been made.¡owever, Tennent and Vilbrandt (20) have determined the diffusion constant of several preparations of thymus nucleic acid the sedimentation rate of which is in close agreement with the values observed in the present study. Assuming that the asymmetry of the molecules is the same in both instances, it is estimated that the molecular weight of the pneumococcal preparation is of the order of 500,000. Examination of the same active preparation was carried out by electropho- resis in the Tiselius apparatusand revealed only a single electrophoretic compo- nent of relatively high mobility comparable to that of a nucleic acid. Trans- forming activity was associated with the fast moving component giving the 4 The Type III antipneumococcus rabbit serum employed in this study was fur- nished through the courtesy of Dr. Jules T. Freund, Bureau of Laboratories, Depart- ment of Health, City of New York. s Studies on sedimentation in the ultracentrifuge were carried out by Dr. A. Rothen; the electrophoretic analyses were made by Dr. T. Shedlovsky, and the ultra- violet absorption curves by Dr. G. I. Lavin. The authors gratefully acknowledge their indebtedness to these members of the staff of The Rockefeller Institute.