Glycerol-Induced Aggregation of the Oligomeric L-Asparaginase Ii from Monitored with Atr-Ftir
Science Direct Working Paper No S1574-0331(04)70473-7
17 Pages Posted: 26 May 2017 Last revised: 23 Dec 2017
Date Written: March 2001
Attenuated total reflectance Fourier transform infrared spectroscopy has been employed for the study of structural composition of aggregates of the oligomeric L-asparaginase II from formed in the presence of glycerol after induction of refolding of the protein . Beside of a perfect coincidence of secondary structure composition of EcA2 determined by FTIR and crystallography (1) it is also shown that secondary structure of protein in asparaginase deposits is similar to that of the native conformation: 20.7% extended, 22.3% disordered, 31.4% helix and 25.6% turn/bend/β sheet. Certain structural similarities in the range of experimental error was observed for all three protein deposits presented in this paper indicating a common stuctural basis for the composition of this types of aggregates. It is also concluded that the partially folded (molten globule like) state(s) constitutes such precipitates and their stabilization is a key factor leading to aggregation. Results presented in this paper might serve as an explanation and good basis for the fundamental theory of protein (oligomers) precipitation by osmotic substances.It has long been known (2) that high molecular weight linear polymers are able to precipitate almost all plasma proteins (mainly oligomers) without denaturation. Although suggesting a new very useful method for a protein fractionation, no acceptable theory was offered and mechanisms underlying this process still remain unknown. L-asparaginase II from has been thought firstly, to undergo simple cooperative transition during unfolding (12-15), secondly, showing strange behaviour for the denaturation of oligomeric proteins (unpublished data) and thirdly, having double-exponantial kinetic profile of refolding as monitored by stopped flow CD (Figure 6). Extensive studies of different types of protein deposits, including those involved in several human diseases (3-8) determine to undestand general forces driving of their formation and to find possible ways to avoid these diseases. It has been found that in particles of protein aggregation substantial amounts of native-like secondary structure are present (9) and was suggested that improper protein association/misfolding involves several types of ordered structures and could be categorised as a native like molten globule, molten globule, pre-molten globule states (10). Therefore, observed precipitation would be caused by a molten globule like equilibrium state, highly populated under physiological conditions(11). ATR-FTIR used in this study seems to be one of the few experimental techniques allowing analysis of protein deposits. The deformation of protein structure due to interaction with an IRE incorporated in this method is negligible. With this type of research we try to describe structure(s) in the glycerol-induced protein deposits for a better understanding of the events occuring at very early stage of protein folding pathway. We would expect to have a powerful test for the elucidation of two-state model transition for oligomeric proteins, better understanding of general features of polypeptide chain, means for the deflecting of various deseases caused by aggregations and new tools for the engineering of very important in the cancer therapy oligomeric enzyme (16).
Keywords: EcA2[WT] - E.coli L-asparaginase II wild type, ATR-FTIR - attenuated total reflectance Fourier transform infrared spectroscopy, MW - molecular weight, PEG - poly ethyleneglycol, IRE - internal reflection element
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