Hasanbašić S, Taler-Verčič A, Puizdar V, Stoka V, Tušek Žnidarič M, Vilfan A, Berbić S, Žerovnik E. Prolines Affect the Nucleation Phase of Amyloid Fibrillation Reaction; Mutational Analysis of Human Stefin B.
ACS Chem Neurosci 2019;
10:2730-2740. [PMID:
30924329 PMCID:
PMC6727212 DOI:
10.1021/acschemneuro.8b00621]
[Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
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Proline
residues play a prominent role in protein folding and aggregation.
We investigated the influence of single prolines and their combination
on oligomerization and the amyloid fibrillation reaction of human
stefin B (stB). The proline mutants influenced the distribution of
oligomers between monomers, dimers, and tetramers as shown by the
size-exclusion chromatography. Only P74S showed higher oligomers,
reminiscent of the molten globule reported previously for the P74S
of stB-Y31 variant. The proline mutants also inhibited to various
degree the amyloid fibrillation reaction. At 30 and 37 °C, inhibition
was complete for the P74S single mutant, two double mutants (P6L P74S
and P74S P79S), and for the triple mutant P6L P11S P74S. At 30 °C
the single mutant P6L completely inhibited the reaction, while P11S
and P79S formed amyloid fibrils with a prolonged lag phase. P36D did
not show a lag phase, reminiscent of a downhill polymerization model.
At 37 °C in addition to P36D, P11S, and P79S, P6L and P11S P74S
also started to fibrillate; however, the yield of the fibrils was
much lower than that of the wild-type protein as judged by transmission
electron microscopy. Thus, Pro 74 cis/trans isomerization
proves to be the key event, acting as a switch toward an amyloid transition.
Using our previous model of nucleation and growth, we simulated the
kinetics of all the mutants that exhibited sigmoidal fibrillation
curves. To our surprise, the nucleation phase was most affected by
Pro cis/trans isomerism, rather than the fibril elongation
phase.
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