Shorter but not more catalytic: an active-site-resolved model of how tau reshapes amyloid-$β$ secondary nucleation

Tau cross-seeding creates a mechanistic puzzle. Tau fibrils accelerate amyloid-$β$42 (A$β$42) nucleation and produce a larger population of shorter A$β$ fibrils, yet homotypic secondary nucleation occurs at rare catalytic sites rather than uniformly over fibril mass. Does making more, shorter fibril