Abstract
Intrinsically disordered proteins (IDPs) are an emerging phenomenon. They may have a high degree of flexibility in their polypeptide chains, which lack a stable 3D structure. Although several biological functions of IDPs have been proposed, their general function is not known. The only finding related to their function is the genetically conserved YSK2 motif present in plant dehydrins. These proteins were shown to be IDPs with the YSK2 motif serving as a core region for the dehydrins’ cryoprotective activity. Here we examined the cryoprotective activity of randomly selected IDPs toward the model enzyme lactate dehydrogenase (LDH). All five IDPs that were examined were in the range of 35–45 amino acid residues in length and were equally potent at a concentration of 50 μg/mL, whereas folded proteins, the PSD-95/Dlg/ZO-1 (PDZ) domain, and lysozymes had no potency. We further examined their cryoprotective activity toward glutathione S-transferase as an example of the other enzyme, and toward enhanced green fluorescent protein as a non-enzyme protein example. We further examined the lyophilization protective activity of the peptides toward LDH, which revealed that some IDPs showed a higher activity than that of bovine serum albumin (BSA). Based on these observations, we propose that cryoprotection is a general feature of IDPs. Our findings may become a clue to various industrial applications of IDPs in the future.
Highlights
The concept of intrinsically disordered proteins (IDPs), known as natively unstructured proteins [1], has been drawing attention, during the past decade [2,3,4,5,6,7]
We hypothesized that the cryoprotective activity of dehydrin-YSK2 is due to its property of intrinsic disorder rather than any unknown “sequence-specific” function
We focused on the human genome-derived IDPs/intrinsically disordered regions (IDRs) because humans are non-hibernating warm-blooded organisms
Summary
The concept of intrinsically disordered proteins (IDPs), known as natively unstructured proteins [1], has been drawing attention, during the past decade [2,3,4,5,6,7]. After the completion of several genome projects for different organisms, the researchers found a large number of IDPs, as well as intrinsically disordered regions (IDRs). These proteins do not seem to adopt any unique and solid conformation under physiological conditions. It has been believed that nascent proteins must undergo a folding process to acquire structure for their appropriate biological functions. The biological importance of IDPs in terms of their specific function should be further examined
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