,m-305 PROTEINS; POLYFEPTIDES

391

SOMS CMF&CTRRISTICS OP A CELL-PREE DNAaee SENSITIVE SYSTRM
INCURPORATING AMINO ACIDS INTO PROTEIN. J. Hcinrich Matthaei*
and Hershall W. Nirenber&*. National Institutes of Health,
Bethesda, Md.

Extracts of e. coli W3100 prepared by grinding cells with
alumina actively in=orate Clkaline into protein. The
extracte were centrifuged at 20,000 x g for 20 minutea.
Remaining intact cells and debris were removed from the super-
natant suspension by centrifuging at 30,000 x g for 60 minutes.
Ribosomes were obtained by centrifuging the supernatant sue-
pension for 2 hours at 105,000 x g. For maxinum incorporation
of Clkaline into protein reactlou mixture.9 require ATP, m
an ATP generating system, a complete amino acid mixture, ribo-
.sorm and a 105,000 x g supernatant solution.  Incorporation
of Cl4-valine into protein proceeds at a rapid rate for 15
minutes at 37O.  Incorporation is markedly inhibited by 50 fig.
chloramphenicol per ml.  10 pg. per ml. DNAnse inhibited
approximately 70% of the incorporation wherean an equivalent
amount of RRAase wan completely inhibitory. Inhibition by
DNAaee cannot be reversed by addition of polyenions. Addition
of a DNAase digest of salmon sperm DRA had no effect upon
incorporation of Clkaline into protein. Although DNAane
markadly inhibits amino acid incorporation into protein, it
ir not known whether intact DNA ia neceasuy for this process.