On the nucleoproteins of avian tubercle bacilli.

The nucleic acids of tubercle bacilli have formed the subject of several studies, among which may be mentioned those by Ruppel (l), Levene (2), and Johnson and his associates (3-5). The work of Mensel and Heidelberger (6) on the fractionation of the proteins of the tubercle bacillus revealed the presence of several protein fractions, rich in phosphorus and in purines, which appeared to be nucleoproteins. The studies of Seibert et al. on tuberculin (7,8) have included experiments on the separation of nucleic acid, present in the crude preparations, from the bioIogicaIly active protein. The main portion of the nucleic acid preparations studied appears to have belonged to the desoxypentose type; the presence of pentose nucleic acid does not seem to have been recorded. In connection with work carried out in this laboratory on bacterial glycogen (9) it was observed that borate buffer extracts of ground avian tubercle bacilli contained, in addition to glycogen, a nucleoprotein fraction giving strong color reactions for desoxypentose. This observation provided an opportunity to study a nucleoprotein obtained from the bacterial cells by a mild extraction process at a low temperature that probably suppressed autolytic reactions. Several other disintegration and extraction methods either were unsuccessful or gave inferior results. The crude nucleoprotein preparations were slightly yellow; they contained a yellow pigment with a blue-green fluorescence and exhibited an absorption peak at 410 rnp, in addition to the typical ultraviolet spectrum of nucleic acids (Fig. 1). Further fractionation made use of the fact that the principal nucleoprotein fraction was insoluble around pH 4 and could not be precipitated by half saturation with ammonium sulfate. By this procedure a desoxypentose nucleoprotein which contained 3.2 per cent P, and was only slightly contaminated with pentose nucleic acid, could be prepared. The crude preparations, however, contained a much larger proportion of pentose nucleic acid which was removed in the course of the fractionation. The spectra of a crude and of a purified specimen are compared in Fig. 2. Not much can be said as yet about the nature of the proteins combined