On β-d-Glucosylamides of l-Amino Acids and of Nicotinic Acid

4,6-O-Benzylidene-D-glucose (I) is converted by methanolic ammonia into 4,6-O-benzylidene-d-glucosylamine (II). N-Acylation of II with the appropriate derivatives of l-amino acids and of nicotinic acid, followed by removal of the protective groups, yields the N-β-d-glucosylamides of l-phenylalanine (IVc), l-aspartic acid (IVd), l-glutamic acid (IVe) and of nicotinic acid (IVf). © 1961, American Chemical Society. All rights reserved

Inhibitors of protein synthesis V. Irreversible interaction of antibiotics with an initiation complex.

The initiation complex (t-complex) formed in a cell-free system (E. coli) from Ac-Phe-tRNA, poly(U) and washed ribosomes in the presence of initiation factors (ribosomal wash) and GTP, contains the Ac-Phe-tRNA bound quantitatively in a puromycin-reactive state. The t-complex is irreversibly inactivated by spiramycin with respect to its reactivity toward puromycin. The inactivated t-complex retains all of the Ac-Phe-tRNA bound, but it does not react with puromycin (2 x10-minus-3M) within 32 min at 25 degrees. In the case of another inhibitor protein synthesis, sparsomycin, the permanently "modified" t-complex not only retains all the bound Ac-Phe-tRNA but it can still react with puromycin. In the continuous presence of sparsomycin (1 x 10-minus-7M) the bound Ac-Phe-tRNA reacts quantitatively at a rate which is one-tenth the rate at which the t-complex reacts with puromycin, at low (6.25 x 10-minus-5M) or high (2 x 10-minus-3M) concentrations. These results are not in agreement with current views according to which aparsomycin binds to the ribosome reversibly at a single site with a KI in the range of 10-minus6-10-minus-7 M and according to which this stie is at the A'-site (puromycin site) of peptidyl transferase