Recent Progress

During the past few years, we have been focusing on the structural and functional characterization of several vertebrate myelin-specific proteins. Below is a brief description of the progress made during 2012.

We have continued our earlier studies on the human myelin protein P2, which is a peripheral membrane protein involved in lipid bilayer stacking into multilayers. With an international network of collaborators, a multidisciplinary approach has been adopted, which combines, for example, high-resolution X-ray crystallography, functional biophysical assays, oriented and synchrotron CD spectroscopy, site-directed mutagenesis, in vivo membrane sheet formation, molecular dynamics simulations, and neutron scattering methods.

The function and in vivo substrate of the myelin-specific enzyme 2´,3´-cyclic nucleotide 3´-phosphodiesterase (CNPase) are still unknown, despite the initial characterization of CNPase as early as 50 years ago. We solved the first crystal structures of the mouse CNPase catalytic phosphodiesterase domain, and have used a structural enzymology approach to gain more information on its catalytic mechanism (Figure 1). Recently, we have obtained a series of high-resolution crystal structures, representing different steps of the reaction mechanism. The data elucidate the reaction mechanism of CNPase, and they indicate that it is an outlier in the 2H phosphoesterase superfamily. The solution structure of full-length CNPase is also now available. We have additionally shown that CNPase binds RNA and calmodulin, and carried out the first experiments on its role in cytoskeletal interactions. In addition to our studies on mammalian CNPase, work on related enzymes from invertebrates and yeast is also ongoing.

Figure 1. How does the 2-fold symmetric CNPase active site achieve stereospecificity?

Juxtanodin is an oligodendrocytic protein that binds directly to actin microfilaments. In order to obtain insights into its function, we carried out structural characterization of juxtanodin, and showed that it is an intrinsically disordered molecule (Figure 2). We are further studying the details of juxtanodin structure, including conformational ensembles and local folding. We will also compare its properties with those of other disordered proteins present in myelin, such as myelin basic protein (MBP).

Figure 2. Solution structure of the intrinsically disordered protein juxtanodin, determined by synchrotron small-angle X-ray scattering.

During 2012, we started strong efforts regarding studies on the structure, function and dynamics of myelin proteins and protein-lipid membrane complexes using neutron methods. The first protein dynamics data from neutron backscattering are currently being analysed, and perdeuterated preparations of two myelin proteins are being used to grow crystals for neutron diffraction experiments. Labelled protein and lipid preparations will also be used to study both protein and lipid dynamics using neutron scattering, as well as membrane structure.

We have also recently taken significant steps forward towards the production and structural characterization of myelin integral membrane proteins and proteins involved in inherited demyelinating neuropathies.
 

Viimeksi päivitetty: 28.10.2016