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Abstract: Synthesis of protein molecules in a cell are carried out by ribosomes. Aribosome can be regarded as a molecular motor which utilizes the input chemicalenergy to move on a messenger RNA mRNA track that also serves as a templatefor the polymerization of the corresponding protein. The forward movement,however, is characterized by an alternating sequence of translocation andpause. Using a quantitative model, which captures the mechanochemical cycle ofan individual ribosome, we derive an {\it exact} analytical expression for thedistribution of its dwell times at the successive positions on the mRNA track.Inverse of the average dwell time satisfies a ``Michaelis-Menten-like-equation and is consistent with the general formula for the average velocity ofa molecular motor with an unbranched mechano-chemical cycle. Extending thisformula appropriately, we also derive the exact force-velocity relation for aribosome. Often many ribosomes simultaneously move on the same mRNA track,while each synthesizes a copy of the same protein. We extend the model of asingle ribosome by incorporating steric exclusion of different individuals onthe same track. We draw the phase diagram of this model of ribosome traffic in3-dimensional spaces spanned by experimentally controllable parameters. Wesuggest new experimental tests of our theoretical predictions.



Author: Ashok Garai, Debanjan Chowdhury, Debashish Chowdhury, T.V. Ramakrishnan

Source: https://arxiv.org/







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