Researchers from the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT), Chinese Academy of Sciences (CAS) release findings of pH-dependent functions and interactions of protein molecules.
In the human body, and those of other organisms, there is a need to maintain a certain pH in order to function. Changes in pH can have serious biological consequences or, as researchers at the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT), Chinese Academy of Sciences (CAS) found, some benefits.
Cellulosomes are extracellular complexes consisting of multiple enzymes, which are associated with the cell's surface. Within the cellulosome cellular structure, the protein molecules dockerin and cohesin were the focus of this study.
“Cellulosomes are complex nanomachines in nature and have great values in biofuel production and biotechnology. This study is an example of the complexity and diversity of cellulosomes,” said study author, Professor Feng Yingang from the Metabolomics Group.
Changes in pH have previously been shown to result in triggering the 'on-off' switches within proteins, affecting it functions. Many of these switches occur naturally and are essential for biological processes within the cell. Biotechnical innovations have been able to apply this function to develop sensors or switches using biomolecules that are pH-dependent.
In this study, published in the journal Science Advances, on the cellulosome assembly of the bacterium Clostridium acetobutylicum, takes this function of proteins further by switching between two functional sites, rather than simply 'on' or 'off', leading to further insights to new applications.
"Our study not only revealed an elegant example of biological regulation but also provides a new approach for developing pH-dependent protein devices and biomaterials for biotechnological application," said Professor Feng.
Researchers found that changing the pH from 4.8 to 7.5 resulted in the cohesin-binding sites on the dockerin molecule switching from one site to the other. This type of switching between two functional sites has not been noted for any interaction between proteins previously.
Nuclear magnetic resonance (NMR) and isothermal titration calorimetry (ITC) were used to describe the distinct features of this interaction. Researchers additionally noted that the affinity, or the attraction between the molecules, was found to change along with the pH. This property is considered is unique, thus far, to C. acetobutylicum bacteria. And unusual when compared to other cohesin-dockerin interactions of other organisms.
This current study and further similar studies following it can potentially be used to create more complex biological switches in synthetic biology and further developments in the fields of biotechnology.
“Next, we will continue to elucidate the structure and regulation of cellulosomes, which could provide interesting novel discoveries and new strategies to increase the efficiency of lignocellulose-based biofuel production,” said Professor Feng.
“Our ultimate goal is to promote sustainable and economical lignocellulose bioconversion and bioenergy production.”