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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 [16 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-pg16.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:	152­RANSFORMATION OF PNEUMOCOCCAL TYPES DISCUSSION The present study deals with the results of an attempt to determine the chem- ical nature of the substance inducing specific transformation of pneumococcal types. A desoxyribonucleic acid fraction has been isolated from Type III pneumococci which is capable of transforming unencapsulated R variants derived from Pneumococcus Type II into fully encapsulated Type III cells. Thompson and Dubos (21) have isolated from pneumococci a nucleic acid of the ribose type. So far as the writers are aware, however, a nucleic acid of the desoxyribose type has not heretofore been recovered from pneumococci nor has specific transformation been experimentally induced in vitro by a chemically defined substance. Although the observations are limited to a single example, they acquire broader significance from the work of earlier investigators who demonstrated the interconvertibility of various pneumococcal types and showed that the specificity of the changes induced is in each instance determined by the par- ticular type of encapsulated cells used to evoke the reaction. From the point of view of the phenomenon in general, therefore, it is of special interest that in the example studied, highly purified and protein-free material consisting largely, if not exclusively, of desoxyribonucleic acid is capable of stimulating unencap- sulated R variants of Pneumococcus Type II to produce a capsular polysac- charide identical in type specificity with that of the cells from which the inducing substance was isolated. Equally striking is the fact that the sub- stance evoking the reaction and the capsular substance produced in response to it are chemically distinct, each belonging to a wholly different class of chem- ical compounds. The inducing substance, on the basis of its chemical and physical properties, appears to be a highly polymerized and viscous form of sodium desoxyribo- nucleate. On the other hand, the Type III capsular substance, the synthesis of which is evoked by this transforming agent, consists chiefly of a non-nitrog- enous polysaccharide constituted of glucose-glucuronic acid units linked in glycosidic union (22).­he presence of the newly formed capsule containing this type-specific polysaccharide confers on the transformed cells all the dis- tinguishing characteristics of Pneumococcus Type III. Thus, it is evident that the inducing substance and the substance produced in turn are chemically distinct and biologically specific in their action and that both are requisite in determining the type specificity of the cell of which they form a part. The experimental data presented in this paper strongly suggest that nucleic acids, at least those of the desoxyribose type, possess different specificities as evidenced by the selective action of the transforming principle. Indeed, the possibility of the existence of specific differences in biological behavior of nucleic acids has previously been suggested (23, 24) but has never been experimentally demonstrated owing in part at least to the lack of suitable biological methods.