Biosynthesis of the peptidoglycan of bacterial cell walls. VI. Incorporation of L-threonine into interpeptide bridges in Micrococcus roseus.

A particulate enzyme system from Micrococcus roseus R2J has been obtained which catalyzes the biosynthesis of a peptidoglycan. The preparation catalyzes the incorporation of L-threonine onto the e-amino group of lysine in the presence of transfer RNA @RNA), supernatant solution, and ATP. Crude l%-L-threonyl-tRNA will substitute for these additional requirements. The threonyl-tRNAs of this organism have been separated into two fractions, each of which participates in both peptidoglycan and protein biosynthesis. The amino acid-coding properties of the two threonyl-tRNAQ in polypeptide synthesis are reported. L-Alanine is also found in the interpeptide bridge of M. roseus R27, but only indirect evidence for the incorporation of L-&nine into the interpeptide bridge following the incorporation of L-threonine could be obtained.