[3dem] from Dr. Christopher Akey, re: postdoctoral position at BUSM

[Christopher Akey]

Members of the 3DEM mailing list-

We are seeking a postdoc to work on the structure and function of 
bacterial and mammalian ribosome-channel complexes. Ideally, this 
appointee will have some experience with cryo-EM work and computing with 
  unix or linux operating systems. The starting date is flexible, but 
could be as early as August 1, 2008 and the initial position would be 
for 3 years.

The structural EM facilities at Boston University School of Medicine are 
excellent and include a TF20 and all ancillary equiptment for cryoEM 
work and image processing. In addition, we have recently added an Oxford 
style holder to compliment our Gatan cryo-holders and a Vitrobot. We 
currently use a 28 processor linux cluster for image processing with 
EMAN and will be upgrading the Beowulf cluster in the coming year.

General details of the lab and our research projects are provided on our 
web pages (http://biophysics.bumc.bu.edu/faculty/akey/index.html).

For additional details please contact Dr. Christopher Akey (cakey at bu.edu).
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			The RCC project-

In humans, the ER translocon assists in the biogenesis of roughly 1/5th 
of the unique proteins encoded in the genome. The ribosome-channel 
complex plays a particularly important role in the targeting of nascent 
membrane proteins.

In a non-translating ribosome-SecY complex, we have shown that a single 
copy of SecY (the Sec61 homolog) binds to the lsu at a primary site that 
encompasses the exit tunnel. Importantly, we were able to dock the loops 
of an atomic model of SecY within the connections between the channel 
and the ribosome (Menetret et al., 2007). The ribosome and the SecY 
loops in this analysis were at ~9.6A resolution.We suggest that this 
copy of SecY is perfectly positioned to capture and translocate the 
nascent chain in an active complex.

In the mammalian system, we obtained a map of the canine 80S ribosome at 
8.7A resolution (within the RCC) and then built an homology model of 
this large protein translation machine, in a collaboration with Dr. A. 
Sali (Chandramouli et al., in press). We then went on to evaluate the 
remarkable, disk-like channel region in this specimen, which contains 
well resolved single copies of both Sec61 and TRAP. This work shows that 
the bacterial and mammalian RCCs have a generally similar architecture 
and this paper is now under review (Ménétret et al. submitted).

To understand this critical system, we are studying RCCs with a defined 
nascent chain from bacteria and from mammalian ER using cryoEM and 
single particle methods to visualize conformational changes associated 
with the presence of the nascent chain in a looped configuration in the 
SecY or Sec61 channel.

This work is a joint collaboration with Drs.Tom Rapoport (HMS) and 
Ramanujan Hegde (NIH), whose groups provide exceptional expertise in the 
biochemical preparation of RCCs and ER translocons.

refs-

Chandramouli, P., Topf, M., Ménétret, J.F., Eswar, N., Cannone, J.J., 
Gutell, R.R., Sali, A., Rapoport, T.A., and Akey, C.W. (in press). 
Structure of the mammalian 80S ribosome at 8.7Å resolution.  Structure

Ménétret, J. F., Schaletzky, Clemons Jr., W.M., Osborne, A.R., Skånland, 
S.S., Denison, C., Gygi, S.J., Kirkpatrick, D.S., Park, E., Ludtke, 
S.J., Rapoport, T.A., & Akey, C.W. (2007). Ribosome binding of a single 
copy of the SecY complex: implications for protein translocation. 
Molecular Cell 28, 1083-1092.

Ménétret, J. F., Hegde, R.S., Aguiar, M., Gygi, S.P.,Park, E., Rapoport, 
T. A., & Akey, C. W. (submitted). Single copies of Sec61 and TRAP 
associate with the non-translating mammalian ribosome.


cheers  C Akey

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        STRUCTURAL ELECTRON MICROSCOPY & CRYSTALLOGRAPHY GROUP
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   Christopher W. Akey, Professor
   Physiology & Biophysics			
   Boston Univ. School of Medicine	
   700 Albany St.			
   Boston, Mass. 02118-2526

   off: 617 638 4051 lab: 617 638 4088
   fax: 617 638 4041
   cakey at bu.edu
   http://biophysics.bumc.bu.edu/faculty/akey/index.html
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