Lipo-amino acid complexes from Bacillus megaterium and their possible role in protein synthesis

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Abstract
VVhen protoplasts of Bacillus megaterium are incubated with [C14]amino acids in growth medium, some of the amino acid is bound tightly in the form of a lipo-amino acid complex or complexes, which can readily be extracted by acetone or methanol and separated from free amino acids chromatographically. The amino acids may be recovered unchanged from the complexes by hydrolysis. When chromatography on silicic acid is carried out, the labelled lipo-amino acids can be eluted with methanol in the "phospholipid fraction." Very little radioactivity can normally be eluted with the neutral lipid fractions. The labelled lipo-amino acid complexes can be further separated into phospholipid and phosphorus-free fractions by chromatography on di-ethylaminoethylcellulose. The labelled lipo-amino acid complexes studied here are not formed when the incubations are carried out in the presence of chloramphenicol or crotoxin, or when the labelled amino acid is added at the time of solvent extraction. Various experiments suggest that the radioactivity bound in both intrinsic and added lipo-amino acid complexes can be used directly for protein synthesis by protoplasts, apparently without prior hydrolysis to free amino acids.