Archaea Have Their Own Rotary Propellers - Evolution News & Views

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Archaea Have Their Own Rotary Propellers

Recently, Lawrence Berkeley National Lab revealed the secrets of the rotary motors that move archaea. It turns out they are different from the engine that powers the bacterial flagellum.

The motility structure of this third domain of life has long been called a flagellum, a whip-like filament that, like the well-studied bacterial flagellum, rotates like a propeller. But although the archaeal structure has a similar function, it is so profoundly different in structure, genetics, and evolution that the researchers argue it deserves its own name: archaellum. (Emphasis added.)
The archaellum bears some resemblance to a structure in bacteria called the Type IV pilus, a kind of "grappling hook" that allows the bacterium to adhere to other cells. But the resemblance ends there; the archaellum is a rotary motor analogous, but not homologous, to the bacterial flagellum. Moreover, the news release said, "This unique motor is highly conserved in all motile archaeal species." So much for evolution.

Structurally, the archaellum appears to show irreducible complexity, in that it has multiple parts contributing to both assembly and motility. One of the key proteins is an ATP-driven unit called FlaI (pronounced "flah-eye"). Inhibition of this protein results in loss of both construction and rotation of the archaellum. Also involved are "a globular C‑terminal domain, or CTD, [which] is connected by a flexible linker to a more variable N‑terminal domain, or NTD, which constitutes a moveable tip."

When bound to ATP, individual FlaI monomers arrange themselves into flat, six-unit rings, hexamers, with the ATPs serving as glue to hold them together. The result resembles a crown, with the CTD units forming the circlet and the free-to-move NTDs as the points.

Seven different conformations were recorded, revealing a dynamic play among the protein's components in a changing, asymmetric assembly. From the detailed images, much of the action of the archaellum motor assembly could be deduced.

The illustrations show a beautifully designed mechanism. Many more parts are needed for function:
The FlaI "crown" both assembles the archaellum and causes it to rotate, but it doesn't work alone. Other important components are the protein FlaJ, which serves as a platform to which FlaI attaches and also forms a kind of bearing that penetrates the cell membrane, and FlaB, the subunits of the archaellum filament itself, plus other helper proteins.
FlaI is also found in bacterial Type IV pili and other secretory systems of microorganisms, but it serves different purposes there. In archaellum construction, FlaI pushes another structural component above the crown upon release of ATP, to allow more components in, causing the archaellum to grow. "The process is similar to the mechanism in a bacterial Type IV pilus, although the resulting structures operate very differently."

The original paper in Molecular Cell states:

Crown interactions and conformations regulate assembly, motility, and force direction via a basic-clamp switching mechanism driving conformational changes between stable, backbone-interconnected moving blocks.
So here scientists have elucidated another irreducibly complex "outboard motor" that is assembled out of complex proteins according to a genetic plan. Yet this motor does not appear to be related to anything else within archaea. Evolutionists would not expect evolutionary sharing between two different kingdoms of life, even if some of the building blocks are the same. Moreover, within archaea, the archaella are "highly conserved" in this supposedly archaic, primitive kingdom of microbes.

Furthermore, the organism they studied, Sulfolobus acidocaldarius, has not just one, but three archaella. Add to that the fact that these motors need to assemble and work in hot springs and highly acidic conditions, and the only logical inference is intelligent design.