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The Cost of Long Catalytic Loops in Folding and Stability of the ALS-Associated Protein SOD1

Yang, Fan ; Wang, Huabing ; Logan, Derek T. LU orcid ; Mu, Xin ; Danielsson, Jens and Oliveberg, Mikael LU (2018) In Journal of the American Chemical Society 140(48). p.16570-16579
Abstract

A conspicuous feature of the amyotrophic lateral sclerosis (ALS)-associated protein SOD1 is that its maturation into a functional enzyme relies on local folding of two disordered loops into a catalytic subdomain. To drive the disorder-to-order transition, the protein employs a single Zn2+ ion. The question is then if the entropic penalty of maintaining such disordered loops in the immature apoSOD1 monomer is large enough to explain its unusually low stability, slow folding, and pathological aggregation in ALS. To find out, we determined the effects of systematically altering the SOD1-loop lengths by protein redesign. The results show that the loops destabilize the apoSOD1 monomer by kcal/mol, rendering the protein marginally... (More)

A conspicuous feature of the amyotrophic lateral sclerosis (ALS)-associated protein SOD1 is that its maturation into a functional enzyme relies on local folding of two disordered loops into a catalytic subdomain. To drive the disorder-to-order transition, the protein employs a single Zn2+ ion. The question is then if the entropic penalty of maintaining such disordered loops in the immature apoSOD1 monomer is large enough to explain its unusually low stability, slow folding, and pathological aggregation in ALS. To find out, we determined the effects of systematically altering the SOD1-loop lengths by protein redesign. The results show that the loops destabilize the apoSOD1 monomer by kcal/mol, rendering the protein marginally stable and accounting for its aggregation behavior. Yet the effect on the global folding kinetics remains much smaller with a transition-state destabilization of <1 kcal/mol. Notably, this 1/3 transition-state to folded-state stability ratio provides a clear-cut example of the enigmatic disagreement between the Leffler α value from loop-length alterations (typically 1/3) and the "standard" reaction coordinates based on solvent perturbations (typically >2/3). Reconciling the issue, we demonstrate that the disagreement disappears when accounting for the progressive loop shortening that occurs along the folding pathway. The approach assumes a consistent Flory loop entropy scaling factor of c = 1.48 for both equilibrium and kinetic data and has the added benefit of verifying the tertiary interactions of the folding nucleus as determined by phi-value analysis. Thus, SOD1 not only represents a case where evolution of key catalytic function has come with the drawback of a destabilized apo state but also stands out as a well-suited model system for exploring the physicochemical details of protein self-organization.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of the American Chemical Society
volume
140
issue
48
pages
10 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:85058109973
ISSN
0002-7863
DOI
10.1021/jacs.8b08141
language
English
LU publication?
yes
id
d19b0df1-80e0-4666-aa45-5e0a31c685a1
date added to LUP
2018-12-18 14:30:03
date last changed
2021-10-03 04:11:32
@article{d19b0df1-80e0-4666-aa45-5e0a31c685a1,
  abstract     = {<p>A conspicuous feature of the amyotrophic lateral sclerosis (ALS)-associated protein SOD1 is that its maturation into a functional enzyme relies on local folding of two disordered loops into a catalytic subdomain. To drive the disorder-to-order transition, the protein employs a single Zn<sup>2+</sup> ion. The question is then if the entropic penalty of maintaining such disordered loops in the immature apoSOD1 monomer is large enough to explain its unusually low stability, slow folding, and pathological aggregation in ALS. To find out, we determined the effects of systematically altering the SOD1-loop lengths by protein redesign. The results show that the loops destabilize the apoSOD1 monomer by kcal/mol, rendering the protein marginally stable and accounting for its aggregation behavior. Yet the effect on the global folding kinetics remains much smaller with a transition-state destabilization of &lt;1 kcal/mol. Notably, this 1/3 transition-state to folded-state stability ratio provides a clear-cut example of the enigmatic disagreement between the Leffler α value from loop-length alterations (typically 1/3) and the "standard" reaction coordinates based on solvent perturbations (typically &gt;2/3). Reconciling the issue, we demonstrate that the disagreement disappears when accounting for the progressive loop shortening that occurs along the folding pathway. The approach assumes a consistent Flory loop entropy scaling factor of c = 1.48 for both equilibrium and kinetic data and has the added benefit of verifying the tertiary interactions of the folding nucleus as determined by phi-value analysis. Thus, SOD1 not only represents a case where evolution of key catalytic function has come with the drawback of a destabilized apo state but also stands out as a well-suited model system for exploring the physicochemical details of protein self-organization.</p>},
  author       = {Yang, Fan and Wang, Huabing and Logan, Derek T. and Mu, Xin and Danielsson, Jens and Oliveberg, Mikael},
  issn         = {0002-7863},
  language     = {eng},
  number       = {48},
  pages        = {16570--16579},
  publisher    = {The American Chemical Society (ACS)},
  series       = {Journal of the American Chemical Society},
  title        = {The Cost of Long Catalytic Loops in Folding and Stability of the ALS-Associated Protein SOD1},
  url          = {http://dx.doi.org/10.1021/jacs.8b08141},
  doi          = {10.1021/jacs.8b08141},
  volume       = {140},
  year         = {2018},
}