Navigation Links
E. coli persists against antibiotics through HipA-induced dormancy
Date:1/15/2009

HOUSTON - Bacteria hunker down and survive antibiotic attack when a protein flips a chemical switch that throws them into a dormant state until treatment abates, researchers at The University of Texas M. D. Anderson Cancer Center report in the Jan.16 edition of Science.

"For antibiotics to work, bacteria have to be growing. Dormancy stops everything, allowing some bacteria to persist after treatment," said senior author Richard Brennan, Ph.D., professor in M. D. Anderson's Department of Biochemistry and Molecular Biology.

By demonstrating in detail how the HipA protein freezes bacterial activity, the researchers have opened the possibility of adding a new class of drugs to therapy against chronic and multidrug resistant bacterial infection.

Working in Escherichia coli, the team solved the structure of HipA and several of its protein complexes down to the atomic level, confirming that HipA is a protein kinase - an enzyme that works by transferring phosphate groups to its target molecules.

HipA is a type of protein kinase that is uncommon in bacteria, said lead author Maria Schumacher, Ph.D., associate professor of biochemistry and molecular biology. While other types of phosphorylation occur in bacteria, HipA phosphorylates proteins at their serine or threonine amino acids. This kinase activity is more commonly associated with eukaryotic cells, which make up animals, plants and fungi, and are generally thought to be more complex.

"These 'simple bacteria' are so complex. We're finding that life is sophisticated at all levels," Schumacher said. HipA is active in other types of gram-negative bacteria, which cause significant human bacterial infections.

Inhibitor could make persistent cells 'vanish'

A number of cancer drugs inhibit kinase activity in specific targets.

"If you stop HipA from working, there essentially is no persistence," Brennan said. "We need to see whether kinase inhibitors will bind to and block HipA's active site. If they work, persistent cells, which are already rare, would vanish." Persistent cells are a one-in-a-million-cells occurrence because HipA is normally kept in check by a protein called HipB.

Persistence is common in "biofilms," bacterial colonies that become attached to a surface in a supportive matrix. Drug-resistant biofilms cause about 60 percent of infections in the developed world, the researchers note.

Overexpression of HipA previously had been associated with cell dormancy and bacterial persistence. Evidence had pointed to kinase activity.

Schumacher, Brennan and colleagues demonstrated the molecular details of HipA's role in multidrug tolerance and HipB's role keeping HipA under wraps in a series of experiments:

  • Using X-ray crystallography to determine and then compare the structures of several HipA complexes, they showed that HipA has a serine/threonine protein kinase fold and that it binds tightly to adenosine triphosphate (ATP), a common characteristic of kinases. Phosphorylation occurs when an enzyme binds to both ATP and to its target protein.
  • Assays of candidate proteins to identify a target for HipA found that EF-Tu interacts strongly with HipA in the presence of ATP. EF-Tu is the most abundant protein in E.coli and plays an essential role in protein synthesis.
  • Subsequent experiments and structural analysis of a HipA/EF-Tu peptide complex indicated that HipA phosphorylates EF-Tu, freezing up the bacteria's protein-making machinery and inducing dormancy.
  • To analyze how HipB normally prevents HipA's function, the team solved the structure of the HipB/DNA/HipA complex. HipB tightly binds two HipA molecules in a sandwich-like structure.
  • HipB does not block HipA's active site, but inactivates it by forcing it into an "open" position. "Proteins move a lot to function, they open and close - think of a clam shell, for example," Brennan explains. To function, a protein must be able to close down on its target molecules - called substrates. The closed state is the active state.
  • HipB also might physically sequester HipA from EF-Tu because the HipA/HipB/DNA complex is located in E. coli's nucleoid, far from the bacteria's membrane where EF-Tu is mainly found.

HipA is free to cause trouble when its ties to HipB are broken; an infrequent occurrence which the authors note is likely caused by proteases tugging the smaller and structurally vulnerable HipB protein out of the complex.

Protein kinases often bind to more than one protein, so there are likely multiple targets for the protein in E. coli and other gram-negative bacteria, Schumacher and Brennan said.

Future research will focus on finding other HipA targets in E. coli, and kinase inhibitors will be examined for their ability to affect HipA function. If a promising inhibitor is found, its structure will be solved to clarify its binding mode and how it might be tweaked to bind HipA even better. "Structure-based drug design should provide the best chance at formulating highly specific and effective drugs against HipA," Schumacher said.


'/>"/>

Contact: Scott Merville
smerville@mdanderson.org
713-792-0661
University of Texas M. D. Anderson Cancer Center
Source:Eurekalert  

Related medicine news :

1. Direct recording shows brain signal persists even in dreamless sleep
2. Raised Breast Cancer Risk Persists After Combo HRT Stopped
3. Facial asymmetry persists despite surgery to correct congenital deformity
4. HIV persists in the gut despite long-term HIV therapy
5. Chronic infection persists by targeting stromal cell network in lymphoid organs
6. AMA Claims Victory With Record Breaking Settlement in Case Against Insurer
7. Report Finds That Raids Are Not an Effective Tool Against Human Trafficking
8. Maslinic acid provides a natural defense against colon cancer
9. Nose-spray vaccine against botulism effective in first tests
10. New Drug May Work Better Against Chemo Side Effects
11. Researchers Report Progress in Fight Against Fat
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
E. coli persists against antibiotics through HipA-induced dormancy
(Date:10/13/2017)... ... 2017 , ... The Visiting Nurse Association (VNA) of Somerset Hills is proud ... and unique items from across the nation, this holiday-themed event will raise funds and ... the VNA. The boutique will be open Saturday, November 4 (10:00 a.m. – ...
(Date:10/13/2017)... ... October 13, 2017 , ... Talented host, ... lowdown on sciatica in a new episode of "Success Files," which is an ... and innovation and investigates each subject in-depth with passion and integrity. , Sciatica ...
(Date:10/12/2017)... ... October 12, 2017 , ... ... for healthcare compliance program management, will showcase a range of technology and learning ... Assisted Living (NCAL) Convention and Expo to be held October 14–18, 2017 at ...
(Date:10/12/2017)... ... October 12, 2017 , ... IsoComforter, Inc. ( ... today the introduction of an innovative new design of the shoulder pad. The ... get maximum comfort while controlling your pain while using cold therapy. By utilizing ice ...
(Date:10/12/2017)... ... October 12, 2017 , ... Dr. Parsa Mohebi, ... a medical article to the newly revamped Cosmetic Town journal section, ... hair transplant procedure known as Follicular Unit Extraction (FUE). , Dr. ...
Breaking Medicine News(10 mins):
(Date:10/5/2017)... 2017  In response to the nationwide opioid ... Surgeons (AAOMS) released prescribing recommendations that urge ibuprofen ... as a first-line therapy to manage a patient,s ... Recognizing the value and importance of ... Prescribing: Acute and Postoperative Pain Management" stresses that ...
(Date:10/2/2017)... INDIANAPOLIS , Oct. 2, 2017  Eli Lilly ... its financial results for the third quarter of 2017 ... a conference call on that day with the investment ... performance. The conference call will begin at ... public can access a live webcast of the conference ...
(Date:9/28/2017)... 2017 Cohen Veterans Bioscience and Early Signal ... wearable and home sensors for real-time monitoring of patients ... a nonprofit organization focused on disruptive health solutions for ... analytical system to record and integrate behavioral, cognitive, physiological ... ...
Breaking Medicine Technology: