The Albers lab tested what happened to S. acidocaldarius when FlaI genes were deleted. Wild-type S. acidocaldarius cells have only one to three archaella on their surfaces, so "hyper-flagellated, hyper-motile" mutants with numerous archaella were created, to make deletion effects readily apparent. Deleting the FlaI gene eliminated the archaella and left the mutants unable to move. But when the researchers reintroduced the FlaI genes, the mutants were able to assemble archaella and use them to swim.
Now the challenge was to find out how FlaI performed its two functions, archaellum assembly and motility, by solving the FlaI protein structure. John Tainer of Berkeley Lab's Life Sciences Division (LSD) and the Scripps Research Institute's Department of Molecular Biology was co-leader of the research with Albers. The stable proteins of S. acidocaldarius, an extremophile able to withstand hot, acidic conditions, make it suitable for x-ray diffraction crystallography, and Tainer's postdoctoral fellow, Sophia Reindl, was able to crystallize the FlaI protein.
To do the crystallography, Reindl used beamline 8.3.1 at Berkeley Lab's Advanced Light Source (ALS), pinpointing the position of all the atoms in the FlaI protein and revealing that it consists of two parts. A globular C terminal domain, or CTD, is connected by a flexible linker to a more variable N terminal domain, or NTD, which constitutes a moveable tip.
As an energy-releasing enzyme the FlaI protein binds to an ATP nucleotide, from which it detaches a phosphate to generate energy leaving adenosine diphosphate, ADP, in its place. After releasing the ADP, the protein binds to a
|Contact: Paul Preuss|
DOE/Lawrence Berkeley National Laboratory