A sequenced genome is fine and dandy, but it doesn't reveal much about the real stuff of life: what proteins do or how they interact. Now, a team of researchers has taken a key step toward exploring this action, tracking where thousands of proteins end up in the cell. Because roughly two-thirds of yeast genes are identical or strikingly similar to human genes, the study could help explain how proteins work in people.
Scientists can glean crucial hints about protein function by determining where in the cell proteins work or whether two or more proteins stick together. A favorite tool for exploring this geography is Saccharomyces cerevisiae, the single-celled yeast that bakers love, because its genes are relatively easy to tag and alter.
That's how biochemist Michael Snyder at Yale University and his colleagues sought to chart the locations of 2744 yeast proteins, more than a third of the known total in yeast. They inserted DNA sequences into the yeast genes so that the proteins the genes built were tagged with a string of peptides that bind with antibodies later added to the cell. When combined with the antibody and examined under a special microscope, the tag glows. After tracing which proteins went where, the group scoured the literature for other yeast protein hangouts. They then compiled an online database for 60% of yeast's proteins. Those results helped them predict the locations of the rest of the proteins. All in all, they report in the 15 March issue of Genes and Development, half the proteins ended up in cytoplasm, a quarter in nucleus, another tenth went to mitochondria, while the rest settled on other parts of cell.
The large scale of the group's effort may ease the process of figuring out how proteins collaborate to run a cell, says yeast biologist Michael Tyers of the University of Toronto in Canada.