期刊
FRONTIERS IN MICROBIOLOGY
卷 8, 期 -, 页码 -出版社
FRONTIERS MEDIA SA
DOI: 10.3389/fmicb.2017.02095
关键词
multidrug resistance; antimicrobial resistance; RND; AcrB; mechanism; pathogens; transporters; crystal structure
类别
资金
- CREST
- Center of Innovation Program (COI) from the Japan Science and Technology Agency (JST)
- Program for the Promotion of Fundamental Studies in Health Sciences of the National Institute of Biomedical Innovation
- Network Joint Research Center for Materials and Devices
- Dynamic Alliance for Open Innovation Bridging Human, Environment and Materials from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT)
- Japan Society for the Promotion of Science (JSPS) [17H03983]
- Japan Agency for Medical Research and Development (AMED)
- Grants-in-Aid for Scientific Research [17H03983] Funding Source: KAKEN
The overexpression of RND-type exporters is one of the main causes of multidrug resistance (MDR) in Gram-negative pathogens. In RND transporters, such as Escherichia coli's main efflux pump AcrB, drug efflux occurs in the porter domain, while protons flow through the transmembrane domain: remote conformational coupling. At the border of a transmembrane helix (TM8) and subdomain PC2, there is a loop which makes a hoisting movement by a random-coil-to-alpha-helix change, and opens and closes a drug channel entrance. This loop is supposed to play a key role in the allosteric conformational coupling between the transmembrane and porter domain. Here we show the results of a series of flexibility loop-mutants of AcrB. We determined the crystal structure of a three amino acid truncated loop mutant, which is still a functional transporter, and show that the short alpha-helix between C beta 15 and the loop unwinds to a random coil in the access and binding monomers and in the extrusion monomer it makes a partially stretched coil-to-helix change. The loop has undergone compensatory conformational changes and still facilitates the opening and closing of the channel. In addition, more flexible mutated loops (proline mutated and significantly elongated) can still function during export. The flexibility in this region is however limited, as an even more truncated mutant (six amino acid deletion) becomes mostly inactive. We found that the hoisting-loop is a highly flexible hinge that enables the conformational energy transmission passively.
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