Tag Archives: usher

Structure of usher pore is available

Structure of usher pore

Some time ago I posted breaking news about solved structure of usher pore. And few days ago it was deposited into PDB as 2VQI (publication appeared in Cell, here’s the abstract). The structure is a beatiful dimer (see above) of 24 stranded beta-barrel, the first of its kind. The paper contains also structures of the whole complex reconstructed based on cryo-EM data.

Interestingly, while the structure of the native dimer is symmetrical, the function of the units is not. Both of twinned pores are involved in alternating recruitment of chaperone:pili-subunit complexes, but only one actually transports pili subunits out. Overall, given large amount of detailed studies on the mechanistic properties of pili transport and formation, this is the best understood translocation process at a structural level.

Read the paper and draw your own conclusions, but for me it changes the way of thinking about protein translocation in bacteria. We learnt a lot on bacterial secretion by observing how similar proteins are involved in fundamentally different processes (for example DNA export and toxin secretion may use the same system). Similarly, usher pore is going to serve as an exemplar for newly found translocation elements.

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Posted by on May 31, 2008 in Papers, Proteins


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Breaking news: structure of usher pore solved

My colleague is at Grenoble on the conference about host-pathogen interactions. Today he sent me important news: Gabriel Waksman (that’s not surprising to anybody interested in structural biology of bacterial pathogenesis) showed structure of usher pore – soon to be published.

Why is that important? Usher is a membrane part of two component system responsible for assembly and transport of fimbriae/pili in gram-negative bacteria – pretty essential element in these organisms. This protein was identified in early 90s (or even earlier) and for quite a while lots of people tried to solve/predict/model its structure. Its structure was assumed to resemble porin – but a large insert right in the middle of beta-barrel gave lots of problems in predicting correct topology. Now we know (at least my colleague saw it, we need to wait) how the final structure looks like and I was also told that its functional aspects have a big relevance to other secretion systems. Have a look on this protein when it’s out (I’ll post definitely about it) – I think you will be surprised even if nuances of host-pathogen interactions are not very appealing to you.

Studying any niche area on the molecular level can be very rewarding. Novel protein fold by itself is not a big deal anymore (it used to be – browse through archives of Nat. Struc. Biol. from several years ago). But putting this novel structure in well known functional context and understanding constrains that led to a new solution is still considered a first-class science.


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