Bacterial motors carefully studied: flagellum (Introduction)

by David Turell , Sunday, September 11, 2016, 00:16 (2995 days ago) @ dhw

A careful study of the flagellum and how it is composed by various molecules. This is what the ID folks thinks is irreducible complexity: - https://www.sciencedaily.com/releases/2016/09/160907113352.htm - "Researchers used biochemical techniques and electron microscopy to uncover the structure of the bacterial MotA protein, which forms part of the propeller motor (flagellum). Three-dimensional analysis found it is composed of a transmembrane component and cytoplasmic domain, while MotA molecules were shown to form stable tetramer complexes with other MotA molecules. These findings will aid understanding of the mechanism underlying energy conversion during bacterial movement. - Heading under the diagram: 
"The three-dimensional structure of a complex of MotA and the flagellar motor structure in a bacterial cell. Many motile bacteria have rotating fiber (flagellum) generating from a cell surface which functions like a screw and create a driving force to move or swim. At the proximal end of flagellum there is a rotary motor which is composed of a rotor and a stator and ions, Na+ or H+, flow into cells by way of the stator. The flows of ions are converted into a rotational force by the interaction between the stator and the rotor. The three-dimensional structure of the MotA complex has been determined from a large number of electron microscope images in this report. - *** - " They found that it can form a structure of four MotA molecules (called a tetramer), which differs in shape from the previously predicted complex. - *** - "The MotA protein spans the bacterial membrane, and has previously been shown to form a tetramer complex with another transmembrane protein, MotB, creating the stator. In this latest work, MotA was expressed and purified from A. aeolicus, and found to be structurally stable. Assessment of its interactive potential revealed it can form a tetramer even in the absence of MotB. - "Electron microscopy showed that the elongated top part of the MotA complex matches the size of the lipid bilayer of the bacterium, suggesting that it represents the transmembrane component. "This region has a globular shape that corresponds to a MotA tetramer fitted inside an aggregate of detergent molecules which were used to purify the protein," first author Norihiro Takekawa says. - "The lower part of the complex has two arch-like regions with spiky projections. "These match the cytoplasmic domain of the MotA protein," corresponding author Michio Homma says. "We predict that its structure will change with the movement of ions through the stator channel and in association with the stator-motor interaction." The shape of the complex differs from that reported for a related protein complex in another bacterium." - Comment: This article and the diagram show how it is impossible to believe this sort of motor developed stepwise. Darwin theory cannot explain this. All the Darwin folks can do is point to precursor parts that were modified.