VESICULAR TRANSPORT - HOW MANY YPT RAB-GTPASES MAKE A EUKARYOTIC CELL/

In eukaryotic cells, protein transport through the secretory and endoc ytic pathways is mediated by vesicular intermediates. Individual trans port steps are regulated by Ras-like guanine nucleotide-binding protei ns, termed Ypt in yeast or Rab in mammals. The complete sequencing of the Saccharomyces cerevisiae genome has revealed the total number of Y pt GTPases in this organism. There is some redundancy among the 11 Ypt proteins, and only those involved in the biosynthetic pathway are ess ential for cell viability.