9BEE

alphaB-crystallin N-terminal IXI variant in a fibril state

Summary for 9BEE

• Entry DOI: 10.2210/pdb9bee/pdb
• EMDB information: 44477
• Descriptor: Alpha-crystallin B chain (2 entities in total)
• Functional Keywords: small heat-shock protein fibril proteostasis cataract, chaperone
• Biological source: Homo sapiens (human); More
• Total number of polymer chains: 2
• Total formula weight: 22050.93

Authors

McFarland, R.,Reichow, S.L. (deposition date: 2024-04-15, release date: 2024-12-11)

Primary citation

McFarland, R.,Noroozi, R.,Miller, A.P.,Reichow, S.L.
Dynamic fibrillar assembly of alpha B-crystallin induced by perturbation of the conserved NT-IXI motif resolved by cryo-EM.
Nat Commun, 15:10336-10336, 2024

PubMed Abstract: αB-crystallin is an archetypical member of the small heat shock proteins (sHSPs) vital for cellular proteostasis and mitigating protein misfolding diseases. Gaining insights into the principles defining their molecular organization and chaperone function have been hindered by intrinsic dynamic properties and limited high-resolution structural analysis. To disentangle the mechanistic underpinnings of these dynamical properties, we ablate a conserved IXI-motif located within the N-terminal (NT) domain of human αB-crystallin implicated in subunit exchange dynamics and client sequestration. This results in a profound structural transformation, from highly polydispersed caged-like native assemblies into an elongated fibril state amenable to high-resolution cryo-EM analysis. The reversible nature of this variant facilitates interrogation of functional effects due to perturbation of the NT-IXI motif in both the native-like oligomer and fibril states. Together, our investigations unveil several features thought to be key mechanistic attributes to sHSPs and point to a critical significance of the NT-IXI motif in αB-crystallin assembly, polydispersity, and chaperone activity.

PubMed: 39609421
DOI: 10.1038/s41467-024-54647-7

Experimental method

ELECTRON MICROSCOPY (3.4 Å)