[Canada] Postdoctoral Position at University Boulevard
Postdoctoral Position Proteomics of Diatom Chloroplast Proteins
A postdoctoral position is available immediately for someone with a good biochemical background and substantial experience in membrane protein purification, to work on the proteomics of diatom chloroplast proteins. Our aim is to use whole-mass proteomics to get a better understanding of how nuclear-encoded proteins are imported across the four membranes that surround these chloroplasts. By determining the N-terminal sequences of mature chloroplast proteins, we will be able to identify the complete transit peptide (stromal targeting) sequences, which are known for very few proteins targeted to chloroplasts derived by secondary endosymbiosis. It will also give us a great deal of information about the proteome of these less-studied chloroplasts.
The work will be carried out in the laboratory of Dr. Beverley Green at the University of British
Columbia, and will involve collaboration with the protein sequencing laboratory of Dr. Julian Whitelegge at UCLA. It will make extensive use of the finished genome sequences of the diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum.
Background. All the algae with Chl c are thought to have acquired their chloroplasts by secondary endosymbiosis, i.e. by engulfing a red alga that already had a well-tamed chloroplast. They include the heterokonts (diatoms, kelps, crysophytes, etc), haptophytes and cryptophytes. In most groups, the chloroplasts are all that remain, now surrounded by two extra membranes derived from the host and endosymbiont plasma membranes. These algae are not minor branches of the Tree of Life but make up a large fraction of ocean biomass and are signficant contributors to global productivity.
The diatoms influence global climate by removing (burying) a significant proportion of the biosphere’s CO2 . Heterotrophic Host Intermediate stage with nucleomorph (Cryptophytes)
Plastid-targeted proteins of these algae have a bipartite N-terminal targeting sequence. The first is an ER signal sequence, which gets them across the chloroplast ER (the fourth membrane surrounding the plastid). The second is a transit peptide (TP) which is similar to plant transit peptides, but has to target precursors across three rather than two membranes: the periplastidal membrane (PPM) and then the outer and inner envelope membranes (OEM and IEM).
BUT: The three major components of the outer envelope translocation apparatus (Toc75,Toc34, Toc159) are completely missing from both finished diatom genomes!!. The essential components of the Tic apparatus (for crossing IEM) are present. So how do these proteins cross the middle pair of membranes before engaging the Tic apparatus? This is what we want to find out.
Contact:
Prof. Beverley R. Green,
Dept. of Botany,
University of British Columbia,
3529-6270 University Boulevard,
Vancouver, B.C., Canada, V6T 1Z4
Phone: 1-604-822-2349 (lab -3613); Fax: 1-604-822-6089
E-mail: brgreen@interchange.ubc.ca
Website: http://www.botany.ubc.ca/faculty/green.htm (being updated!)
