Amino Acids, Peptides and Proteins
NMR investigation of disulfide containing peptides and proteins
Published:12 Nov 2013
Katalin E. Kövér, Gyula Batta, 2013. "NMR investigation of disulfide containing peptides and proteins", Amino Acids, Peptides and Proteins, Etelka Farkas, Maxim Ryadnov
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We give a short overview of the literature covering a period from 2011 to 2013 concentrating rather to peptides and small proteins and some recent advances in solution NMR technology devoted to disclosing the structure of disulfide peptides and proteins. Disulfide peptides and proteins are not only interesting for their own structural curiosities and biological significance. They are important models for understanding the dynamic nature of proteins including folding/unfolding events. Solution NMR is especially suitable for studying molecular motions in an enormously big timescale, ranging from ps to days. The analysis and interpretation of 15N-relaxation for example, has become an everyday practice either by model-free or reduced spectral density methods. Combining these data with contemporary extreme long-time (ms range) in-silico molecular dynamics calculations is a fascinating possibility to better understand the soft or “fuzzy” protein world. There are so many disulfide peptides and proteins in the databases, that it is nearly hopeless to cover all, even for a relatively short period of time. Approximately 10% of the mammalian proteins contain disulfide bonds. Apparently, structure-dynamics-folding-function studies are in the focus of the research of new entities. Parallel to the increasing number of new disulfide proteins and peptides, capabilities of instrumentation have been extended significantly. In the PDB database http://www.rcsb.org/pdb/home/home.do among the 21.000 disulfide containing structures nearly 1900 were solved by NMR, and most of them belong to small proteins (600) or peptides (130). Among them are knottins (small inhibitors, toxins, lectins, 272), snake toxin-like (disulfide-rich fold, nearly all beta, 62), insulin-like (nearly all alpha, 40), defensin-like (disulfide-rich, nearly all beta, 27), BPTI-like (disulfide-rich alpha + beta fold, 20), Kazal-type serine protease inhibitors (16), complement control module/SCR disulfide-rich all beta (16), other (151). The scope of a recent review1 covered the secreted human cysteine-rich mini-proteins. Analysis of their molecular targets showed that these mini-proteins are frequently ligands for G protein- and enzyme-coupled receptors, transporters, extracellular enzyme inhibitors, and antimicrobial peptides. As a conclusion, cysteine-frameworks must play an important role in human biology. Post-translational cleavage or the formation of disulfide bonds are now being identified in cancer-related proteins and an opinion was published2 how these allosteric bonds could be targets for new therapies. The importance of NMR and protein structure in drug design and application to cyclotides and conotoxins was underlined in another overview.3 Conotoxins are disulfide-rich peptides from the venoms of marine cone snails, and they may interact with ion channels, transporters and other receptor sites. For structure determination of disulfide peptides and mini-proteins NMR has distinct advantages if compared to X-ray crystallography.