Diving deeper into protein function The High Temperature Requirement A (HtrA) family of proteins plays an important role in protein quality control, and loss of function is directly associated with several serious diseases. We spoke to Dr Björn Burmann about his research into how these proteases work on the molecular level, which could lay the foundations for further exploitations of these proteases in the future. The HtrA family of proteins are thought
HtrA proteases
to play a significant role in the development and progression of several different diseases. Experimental evidence suggests that loss of proteolytic activity is a key factor in certain types of cancer, as well as some neurodegenerative conditions. As an Assistant Professor at the Wallenberg Centre for Molecular and Translational Medicine, Dr Björn Burmann aims to dive deeper into the structure and function of these proteins. “In my lab we are looking in detail into how they actually work on the molecular level,” he outlines. There are four of these proteins in humans within the HtrA (high temperature requirement A) family, and they function as proteases, helping to break down or cleave proteins and aggregates. “One of the main functions of proteases is to kind of chop down proteins, to degrade them,” explains Dr Burmann.
There is still much to learn about these HtrA proteases however, in particular how their function is modulated by interactions with aggregated proteins, a topic central to Dr Burmann’s research. One part of this work involves using nuclear magnetic resonance (NMR) spectroscopy in solution to gain deeper insights into these proteases. “We do a lot of biochemistry and use other biophysical analysis techniques to study protein interactions and their consequences. In order to get information on the atomic level about these proteins as well as structural and dynamical changes, we need to use NMR,” outlines Dr Burmann. This is a structural biology technique allowing Dr Burmann and his colleagues to analyse proteases in great depth. “We can look at the proximity of amino-acids in a 3-dimensional structure for example. With NMR we get a picture of how a protein behaves in solution,” he says.
A number of other techniques are also being utilised in research, including X-ray crystallography and cryo-electron microscopy. These techniques are highly complementary to NMR spectroscopy, says Dr Burmann. “We’re making use of these different techniques, combining them in the most convenient way possible to answer biological questions,” he outlines. A lot of attention in Dr Burmann’s group is focused on the HtrA2 protease in particular, which is involved in triggering apoptosis, the controlled cell death program. “HtrA2 resides in the membrane of mitochondria. The signal which leads to the initial cleavage and which effectively activates this protein is unknown,” he explains. “On a cartoon level, it is known that HtrA2 has to be effectively detached from this membrane through protein cleavage.” Preparing E. coli cultures to express recombinant HtrA2.
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