The Pathogenic Mutation T182A Converts the Prion Protein into a Molten Globule-like Conformation Whose Misfolding to Oligomers but Not to Fibrils Is Drastically Accelerated
Authors: Jayant B Udgaonkar
Jogender Singh
Journal: Biochemistry (2016)
Discipline: BIOLOGY & BIOCHEMISTRY
Keywords: pathogenic mutations; familial prion diseases; prion protein; misfolding; T182A mutation
Affiliations: National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India

Abstract:  Delineation of the effects of pathogenic mutations linked with familial prion diseases on the structure and misfolding of prion protein (PrP) will be useful in understanding the molecular mechanism of PrP misfolding. Here, it has been shown that the pathogenic mutation T182A causes a drastic reduction in the apparent cooperativity and enthalpy of unfolding of the mouse prion protein (moPrP) under misfolding-prone conditions by converting the protein into a molten globule (MG)-like conformation. Hydrogen-deuterium exchange studies in conjunction with mass spectrometry indicate that the T182A mutation disrupts the core of the protein, thereby increasing overall structural dynamics. T182A moPrP is shown to misfold to oligomers very much faster than does wild-type (wt) moPrP but to misfold to fibrils at a rate similar to that of wt moPrP. This observation suggests that oligomers are unlikely to play a productive role in the direct pathway of aggregation from monomer to fibrils. The observation that fully folded T182A moPrP has a MG-like structure, and that it misfolds to oligomers much faster than does wt moPrP, suggests that a MG-like intermediate, whose structure resembles that of fully folded T182A moPrP, might be populated early on the pathway of misfolding of wt moPrP to oligomers. 

Retracted: No

PubPeer comments:
  Can authors check the original data? , 
 It has been pointed out that the values shown in Figure 5, for percent deuterium incorporation into three sequence segments, 149-153, 154-167, and 159-166, of T182A moPrP are similar for some time points. This is certainly true, but the values are not identical for the three segments. The attached file has the values. The differences in values are small compared to the size of the symbols in the Figure. Sequence segment 159-166 is part of sequence segment 154-167, and it is perhaps not surprising that both have similar values for deuterium incorporation in the mutant protein. Segment 149-153 is adjacent to segment 154-167, and has only a slightly higher deuterium incorporation rate in the mutant protein than the latter (attached image).  , 
 #2 Authors provided the mean values for their plot. it is very surprising that from multiple independent experiments they obtained same mean values of 95.5319 for both 60 min and 720 min time point (the time difference of deuterium incorporation is around 11 hours. This coincidence is very unlikely happen. , 
 #3 Following AR s comment, would you consider of 96.1702 at the 120 and 480 minutes to also seem unlikely? , 
 #4 That is also very valid point, Thank you Atheropla Decaspila for pointing out this , 
 The % deuteration values were seen to vary between 95 and 96% at saturation (30 minutes onwards), and were very similar as expected. Occasionally, values were identical because they were computed from the mass values of the exchanging peptide that were determined to a precision of 0.01 Da. , 
 This sounds a little bit strange. The authors are mentioned in the paper that these data points are from three independent experiments and Errors represent the standard deviations determined from three independent experiments. If this is true then it is very unlikely that authors get exactly identical numbers for different time points, even these values are matching to the fourth decimal point. Authors mentioned that the precision of 0.01 Da. Additionally, the deltaG values reported for wt moPrP in this paper contradict with the deltaG values published by same authors under similar conditions. Here again these measurement values are calculated from three independent experiments. ,