Protein helps notorious bacteria escape stomach acid

March 30th, 2009 - 6:33 pm ICT by IANS  

Washington, March 30 (IANS) A tiny protein helps notorious bacteria E.coli evade the ravages of stomach acid, according to a discovery of researchers.
Stomach acid helps in digestion of food, killing disease-causing bacteria. One way acid kills bacteria is by causing their proteins to unfold and stick together in much the same way that heating an egg causes its proteins to form a solid mass.

Just as it is virtually impossible to “unboil” an egg, it is also very difficult for bacteria to dissolve these protein clumps, so bacteria and most living things can die when exposed to acid or heat.

However, a tiny protein called HdeA protects disease-causing bacteria like the E.coli from the ravages of stomach acid, and James Bardwell and his co-workers at the University of Michigan (UM) have described how this protein works.

Like other proteins, HdeA unfolds and becomes more flexible when exposed to acid. But in a clever twist, the unfolding process that inactivates most other proteins activates HdeA.

Once unfolded, this plastic protein moulds itself to fit other bacterial proteins that have been made sticky by acid-induced unfolding.

“Just as plastic wrappers prevent candies from sticking together, HdeA prevents the unfolded proteins from sticking together and forming clumps,” said Bardwell, professor of molecular, cellular and developmental biology at the UM.

Post-doctoral fellow Tim Tapley of UM, who led the research, said: “HdeA directly senses acid and changes from its inactive to active form within a fraction of a second.”

Instead of becoming completely unfolded in response to acid and sticking to itself, HdeA is only partially unfolded. It then uses the flexibility it gains through partial unfolding to rapidly become plastic enough to adapt to and bind various damaged proteins, said a Michigan release.

This helps E.coli evade the otherwise deadly effects of stomach acid.

These findings were published online in the Proceedings of the National Academy of Sciences in March.

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