Enhanced Diagnostic Tools
Post-translational modifications of proteins play critical roles in the regulation and function of many known biological processes. Proteins can be post-translationally modified in many different ways, and a common post-transcriptional modification of lysine involves methylation. Lysine can be methylated once, twice, or three times by lysine methyltransferases. The transfer of methyl groups from S-adenosyl methionine to histones is catalyzed by enzymes known as histone methyltransferases. Histones which are methylated on certain residues can act epigenetically to repress or activate gene expression.
Histones can undergo many modifications. One of these modifications, lysine methylation, has important functions in many biological processes that include transcriptional regulation, heterochromatin formation, and even X-chromosome inactivation.
Histone lysine methylation occurs on histones H3 and H4, and can signal either transcriptional activation or repression, depending on the sites of methylation. Methylation on the same site can also lead to different outcomes depending on the number of methyl groups added to lysine’s side chain.
The methylation affects the binding of surrounding DNA to those histones, because the effective radius of the positive charge is increased, reducing electrostatic attraction with the negatively charged DNA. Also, methyl groups themselves are hydrophobic and will alter the structure of water in the vicinity.
Though widely associated with histones and gene expression, lysine methylation has also found other uses such as creating protein crystallizations crucial in X-ray structure determination.
Crystallography is used widely to solve atomic detail of structures of macromolecules. However, success is dependent on obtaining diffraction-quality crystals. The hydrophobic nature of methylated lysines will favor protein-protein interactions and drive formation of certain protein complexes. The change in chemistry of the free amide group also affects other biophysical properties, like reducing the solubility of proteins and sometimes changing the oligomeric state. The effects of lysine methylation on behavior of proteins in crystallization can be complex; but can significantly improve success rate.
With Lysines methylation being one of the most common post-translational modifications, BSI has dedicated great amount of resources to developing and offering all of the methylated lysine modifications. BSI is able to produce peptides with mono-methylated Lysine, Di-methylated Lysine, and tri-methylated Lysines. All modified peptides have to pass stringent QC and QA procedures and include MALDI-TOF, analytical HPLC, and C of A documentation.
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Martin, Zhang. The Diverse Functions of Histone Lysine Methylation. Molecular Cell Biology, Volume 6, 838- Nov 2005 Nature Reviews
Walter, et al. Lysine Methylation as a Routine Ways & Means Rescue Strategy for Protein Crystallization Structure 14, 1617–1622, November 2006 Elsevier 849
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