2002 Annual Science Report
University of Washington Reporting | JUL 2001 – JUN 2002
Origin of the Eukaryotic Cell: Implications From Bacterial Tubulin in the Division Verrucomicrobia
We have found genes for tubulin in four species of Prosthecobacter, a genus of the bacterial division Verrucomicrobia. This is the first report of tubulin genes in a prokaryotic organism. Two tubulin genes are found, including BtubA and BtubB, which appear to be homologs for alpha- and beta-tubulin genes of eukaryotes, respectively. The genes occur in an operon along with a gene for light chain kinesin. Reverse Transcription Polymerase Chain Reaction (RT-PCR) has been used to demonstrate that the genes are being expressed. Using deduced amino acid sequences, we have constructed the 3-dimensional proteins. The BtubA and BtubB do not appear to form a dimer as is found in eukaryotic tubulin. This finding is consistent with the apparent absence of microtubules in the cells of Prosthecobacter dejongeii when observed in thin sections.
The discovery of tubulin in bacteria raises questions as to their origin. They could have been transferred horizontally from a eukaryotic organism to these bacteria or vice versa. The goal of our current research is to better understand the origin of the bacterial tubulin genes that are very distantly related to those from eukaryotes indicating that the transfer, if it occurred, must have happened a long time ago.
We are currently preparing a paper for publication on our findings.
PROJECT MEMBERS:James Staley
RELATED OBJECTIVES:Objective 2.0
Develop and test plausible pathways by which ancient counterparts of membrane systems, proteins and nucleic acids were synthesized from simpler precursors and assembled into protocells.
Expand and interpret the genomic database of a select group of key microorganisms in order to reveal the history and dynamics of evolution.