Bacterial motors carefully studied:flagellum enzymes (Introduction)

by David Turell , Tuesday, September 12, 2017, 18:21 (2628 days ago) @ David Turell

Found on the surface of flagella, this enzyme can attack the organism the bacterium is infecting. This adds to the complexity of the flagellum which is a tiny motor:

https://www.sciencedaily.com/releases/2017/09/170912093059.htm

"Researchers have discovered a new class of enzymes in hundreds of bacterial species, including some that cause disease in humans and animals. The discovery provides new insights into how bacteria invade their hosts.

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"'What we found in this case is that many bacteria have repurposed their flagella to function as protein-degrading enzymes. There are thousands of these enzymes, making this potentially one of the largest enzyme structures known."

"Bacterial flagella are filaments composed of around 20,000 proteins that link up together and form structures about 10 micrometers long -- roughly one-tenth the width of a human hair. While they can differ structurally, most flagella help with propulsion, and in some cases, they can attach bacteria to host cells. The discovery of flagella as enzymes means that some of them can also break down tough bonds in cells and tissues.

"We think that these enzymatic flagella may help some bacteria degrade and move through viscous environments. Interestingly, scientists have tried engineering flagella with this functionality before, but until now, we didn't know that nature already did this," said Doxey, a member of the Centre for Bioengineering and Biotechnology at Waterloo.

"To test whether these new enzymatic flagella are active, scientists examined Clostridium haemolyticum, a pathogen that's highly fatal in cows and sheep, and isolated the flagella. This pathogen has numerous flagella on one cell. They found that the flagella are capable of breaking down proteins found in cow liver -- precisely where the organism infects.

"The researchers also found the enzymes in bacteria that inhabit the human gut. Further research is needed to determine whether they play a beneficial or harmful role in humans."

Conclusion from the study: http://www.nature.com/articles/s41467-017-00599-0

"our findings provide a fascinating and multilayered story of molecular evolution, involving not only protein domain recombination, but also lateral gene transfer. First, a collagenase-related gene appears to have inserted into a flagellin hypervariable region, presumably within a collagenase-containing lineage such as Clostridium. This is consistent with numerous studies that have documented intragenic recombination in flagellins, which serves as a mechanism for antigenic diversification. It is reasonable to assume that this domain insertion likely happened after the evolution of microbial collagenase and MMP-like proteins. The proteolytic flagellin gene then spread to other microorganisms through lateral transfer "

Comment: Enzymes are giant complex molecules. This one contains zinc. This adds to the known complexity of flagella. It cannot have developed by chance evolution, as it is irreducibly complex.