Date/Time Date(s) - 29/02/20123:30 pm - 4:30 pm
Title: Efficiency in the Cell: How Cells Make Proteins Rapidly While Working to a Budget
Speaker: Dr. Paul Higgs, McMaster University
Institute:
Location: ABB 102
Description:
A biophysicist might view a cell as a factory that makes macromolecules. Like all factories, a cell requires energy to work, and energy comes at a cost. Cells that make efficient use of their resources grow and divide faster. Processes that are costly to the cell will be under natural selection, and should evolve towards increased efficiency. One of the most important processes in the cell is translation, the process by which proteins are synthesized by ribosomes. A ribosome is a molecular machine that decodes the genetic information from an mRNA sequence and constructs a protein. Ribosomes bind to one end of a mRNA and move forward, adding one amino acid to the protein for each codon (three nucleotides). One way for cells to be efficient is to make proteins that are cheap; hence, cells tend to make more frequent use of amino acids that are cheaper to synthesize. Another way to be efficient is to speed up the translation process, so that proteins can be made faster with a limited number of ribosomes. The time taken by the ribosome per codon depends on the codon used. Sequence analysis of many bacterial genomes shows that faster codons are indeed preferred. If more than one ribosome is bound to a single mRNA, these follow one another like trains along the same track. Regions of slow codons can lead to ribosomal traffic jams. We will discuss the application of particle hopping models from statistical physics to the problem of ribosome dynamics and traffic jams. This talk is written for the CAP lecture series to physics undergraduates. It will be an example of how those with a background in physics can build quantitative models that help in understanding important questions in biology and molecular evolution.