Heme Post-translational Modifications Impact On The Structure And Function Of Myoglobin

Proteins are the basis of biological functions in life system. Living systems can perform a variety of functions in the natural environment,through a series of proteins' interaction. A great many proteins belong to metalloproteins or metalloenzymes. These metalloproteins containing metal ions or metal prosthetic groups and they are indispensable part of proteins to perform variety of biological functions. Among the metal protein, we selected the heme-containing as a prosthetic group of hemoproteins to be our object of study, focusing on myoglobin. Differences in the structure and the interactions between heme and protein matrix of hemoproteins cause different functions for proteins. One of method to regulating these functions is the heme-protein cross-link, an important post-translational modification.In this thesis, when we study F43 Y Mb, a sperm whale myoglobin mutant, a novel C-O covalent bond was found between heme vinyl group and tyrosine hydroxyl group. By combination of X-ray crystallography, protein mass spectrometry, ultraviolet spectroscopy, electron paramagnetic resonance spectroscopy and other methods to explore the effects of covalent linkage to proteins' structures and functions. The study found that F43 Y Mb' ability of H2O2 activation is almost 100-fold higher than wild-type myoglobin under the same conditions. Moreover, this study showed that with an additional distal His29 introduced in the heme pocket, the double mutant L29H/F43 Y Mb can form two distinct forms under different protein purification conditions, with and without a novel Tyr–heme cross-link. Therefore, we made a direct structural and functional comparison in the same protein scaffold to study the influence of cross-link. These progresses have not only enhanced our knowledge of how PTMs fine-tune the SPRF relationship of heme proteins, but also provided us new approaches for design of artificial heme proteins with advanced functions.