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Researchers discover three disease-causing genes in Salmonella

February 08, 2016

Perhaps the mutant strains don't know when to quit. Wild-type Salmonella might enter a state of suspended animation to weather harsh conditions, whereas the mutants fail to respond properly to environmental stress. The fact that the mutants continue to respire when they are in dire straits might lead to the production of toxic oxygen-containing compounds.

"This might explain," the authors suggested, "why the mutants are broadly sensitive to a large number of unrelated compounds and cellular stresses."

The researchers also noticed a resemblance between the astounding manner in which the poxA gene modifies the bacterial elongation factor to regulate stress resistance, and the way a similarly acting factor is regulated in plant and animal cells.

During the manufacture of a protein, transfer RNA, also called tRNA, normally places an amino acid at the end of a growing chain of protein building blocks. A certain type of enzyme normally hands the tRNA the amino acid for it to place. However, in this study, researchers have shown for the first time that the poxA enzyme steps in and directly attaches an amino acid to the Elongation Factor P protein, rather than to the tRNA.

Fang said, "Sometimes it seems as if the most basic discoveries in biology have already been made. It was fun and unexpected to learn something new about a process as fundamental as protein synthesis."

"This is an interesting illustration of molecular evolution," Fang continued. "This essential, but previously unrecognized mechanism, for regulating the production of proteins appears to have been conserved over evolutionary time and continues to take place in cells belonging to all five kingdoms of life."

Future studies in his lab will address the specific reasons behind the defective stress response in poxA- and yjeK-deficient bacteria and the explanation for its different effects on the amounts of individual proteins. The lab will also look further into the roles of the normal poxA and yjeK proteins, the intriguing way in which the bacterial elongation protein is modified, the apparent universality of this protein-modifying mechanism in living cells and its conservation throughout the course of evolution.

Source: University of Washington