Preparation Of Cell-free Extracts Research Articles

The metabolic functions of vitamin B 12: IV. Binding of vitamin B 12 by ribosomes in Lactobacillus leichmannii

The exogenous vitamin B 12 utilized by Lactobacillus leichmannii is bound almost exclusively in the ribosomes. This conclusion is based upon the following evidence: Centrifugation of [ 60Co]vitamin B 12-containing cell-free at 144000 × g caused radioactivity to sediment with the ribosome fraction. Centrifugation of the ribosomes in sodium deoxycholate or 50% sucrose did not release bound vitamin. Centrifugation in a sucrose-density-gradient system showed that various ribosomal subunits are equally labelled by [ 60Co]vitamin B 12. Chromatography on DEAE-cellulose, using a NaCl-gradient-elution system, produced congruent elution profiles of radioactivity and ribosomal material. Preparation of cell-free extracts by alumina grinding caused the disintegration or dissociation of [ 60Co]vitamin B 12-containing ribosomes. CsCl treatment also altered ribosomal structure and caused the release of a ribosomal vitamin B 12-binding protein.

Lysis and preparation of stable 'protoplasts' of Xanthomonas phaseoli (XP8).

Techniques are described for lysing cells of the Gram-negative organism Xanthomonas phaseoli with lysozyme and with penicillin. In the presence of a supporting medium 'protoplasts' are formed which may be stabilized by the addition of magnesium ions at the appropriate time. The application of these methods to the preparation of cell-free extracts of this organism is discussed.

The mechanism of allantoin catabolism by yeast

1. 1. A procedure for the preparation of cell-free extracts of allantoinase from yeast was described. 2. 2. Saccharomyces cerevisiae Hansen required much more biotin for growth on allantoin, allantoic acid, and urea than for comparable growth on all other known sources of nitrogen. This increased biotin requirement was associated with the mechanism of assimilation of these compounds. The requirement of S. cerevisiae for biotin decreased in the order allantoin, allantoic acid, urea, a finding suggestive of the conversion of allantoin into urea via allantoic acid.