  Many ribosomes simultaneously move on the same messenger RNA (mRNA), each
separately synthesizing the protein coded by the mRNA. Earlier models of
ribosome traffic represent each ribosome by a ``self-propelled particle'' and
capture the dynamics by an extension of the totally asymmetric simple exclusion
process (TASEP). In contrast, here we develope a theoretical model that not
only incorporates the mutual exclusions of the interacting ribosomes, but also
describes explicitly the mechano-chemistry of each of these individual cyclic
machines during protein synthesis. Using analytical and numerical techniques of
non-equilibrium statistical mechanics, we analyze this model and illustrate its
power by making experimentally testable predictions on the rate of protein
synthesis in real time and the density profile of the ribosomes on some mRNAs
in E-Coli.
