Cellular machines continuously produce long polypeptide chains, the proteins. In order to properly fulfill its cellular function, a protein must however first adopt its correct spatial structure.
In each cell there are molecular helper proteins called chaperones. They take care of the immature proteins to help them in the folding process and thus preventing errors.
The scientists have discovered how two chaperones (Skp and SurA) in the gut bacterium E. coli ptrotect the membrane protein FhuA during transport and assist it insertion into the membrane.
In order to reach its goal in the outer membrane, FhuA uses the help of several chaperones. Under the protection of the chaperones, within a millisecond, FhuA constantly changes its structure. It thus explores energetically favorable conformations which enable the stepwise insertion and folding of individual protein segments into the membrane.
With the insertion of the final protein segment, FhuA acquires its mature and functional barrel structure. Left unprotected, FhuA would fold incorrectly and finally aggregate.