Biological complexity: bacterial garbage systems (Introduction)

by David Turell , Thursday, October 08, 2015, 18:23 (3334 days ago) @ David Turell

Bacteria use a series of molecular activities to rid themselves of used proteins:-http://phys.org/news/2015-10-protein-cleanup-factors-bacterial-growth.html-"Biochemists have long known that crucial cell processes depend on a highly regulated cleanup system known as proteolysis, where specialized proteins called proteases degrade damaged or no-longer-needed proteins. These proteases must destroy their specific targets without damaging other proteins, but how this orderly destruction works is unknown in many cases-"Lead author Kamal Joshi, a doctoral candidate in the Chien lab, conducted experiments in the model bacterium Caulobacter crescentus. In this species, the ability to grow and replicate DNA is regulated by ClpXP, a highly conserved protease that in many bacteria allows them to cope with stressful environments such as the human body. Understanding how ClpXP is controlled could open a path to antibiotics that inhibit harmful bacteria in new ways.-"Chien explains that one of the long-standing mysteries in the field is how proteolysis controls Caulobacter growth. "The odd thing is that ClpXP is always present during different growth stages, but only destroys its target proteins at a specific time," he says. This led his group to think, "There must be a missing factor that we couldn't see, because something has to come on the scene to accomplish this. There was some genetic evidence pointing to certain additional proteins, but we didn't know how they worked."-***-"His lab took a biochemical approach to the problem, purifying all available proteins and designing experiments to query how they interacted and what functions were affected in their presence or absence. In this way, "Kamal found that the ClpXP protease could not by itself destroy the target proteins," Chien says. Instead, "he found that the additional regulatory proteins we had detected were controlling different parts of the process."-"Further, Joshi found that these newly identified regulatory adaptors worked in a step-wise hierarchical way. The first adaptor was directly responsible for degrading a handful of proteins, but it could also recruit an additional adaptor that would deliver a different set of proteins and bind even more adaptors. Working with the Viollier lab from the University of Geneva, Switzerland, the researchers found scores of additional protease targets that were destroyed in this hierarchical way."
 (my bold)-Comment: Basically an automatic series of molecular actions. Remember that enzymes are enormous molecules, not likely to have developed by chance.