autonomy v. automaticity: protein to protein reactions (Evolution)

by David Turell , Tuesday, September 25, 2018, 23:16 (2032 days ago) @ dhw

This article shows how protein receptors trigger a reaction which is simple as one molecule automatically follows another to achieve the result, in this case a spore formed by a bacterium:

https://phys.org/news/2018-09-bacteria-password-sporulation-hasnt-billion.html

"When it comes to changing their passwords, bacteria are just as bad as you and me—maybe even worse. A Carnegie Mellon University research team has found that despite 2.7 billion years of evolution, bacteria are still using the same "password" to initiate the process for making spores.

"Bacteria make spores when times are tough. A protective shell forms around dormant cells to let them withstand harsh conditions like heat, acidity and radiation. Understanding sporulation has implications for many fields, including health care. For example, the spores of C. difficile can survive hand sanitizer, making that bacterium the leading cause of hospital-acquired infections.

"Bacteria use "plug-and-play" signaling networks to sense and respond to environmental challenges. A sensor protein recognizes an environmental signal and passes a message to an activator protein, which turns on the appropriate response. Each sensor-activator pair has a specific set of amino acids that act like a password, which ensures that the sensor passes the message to the correct activator.

"In the case of the sporulation network, a sensor protein recognizes environmental threats and alerts an activator protein that controls sporulation. The plug-and-play nature of signaling networks makes it easy for bacteria to adapt in a constantly changing world by integrating new sensors into the sporulation network. A sensor that recognizes a new challenge can turn on sporulation, as long as it has the password for the sporulation activator.

***

"To better understand these changes, study co-author Philip Davidson built artificial four-protein networks in test tubes, each with different combinations of the proteins found in the four-protein sporulation networks. He was able to replace any protein in a Bacillar four-protein sporulation network with the corresponding protein from a Clostridial four-protein network, and vice versa, and the activator still got the message. This shows that Clostridia and Bacilli are still using the same passwords as their ancestor that lived 2.7 billion years ago.

"'It's like your home wireless network. When you first got it, you set up a password and put it in all of your wireless devices. Over the years, you got new computers and smart phones, or had visitors who needed to use the wireless network. If you changed the password, the old devices wouldn't work, which would be a hassle. So, you continue to use the old password to ensure that everyone could still access the system," Durand said. "Philip's experiments show that the Clostridia and the Bacilli get stuck in the same rut when it comes to changing passwords as we do.'"

Comment: A perfect example of cellular automaticity, no intellectual action required by the cell, and the mechanism is about 2.7 byo.