Cellulosomes are multi-enzyme assemblies that enable anaerobic bacteria to efficiently degrade plant cell walls, with scaffoldins organized by cohesin-dockerin interactions whose mechanical properties are critical for anchoring catalytic subunits under load. In Acetivibrio cellulolyticus , proximal bridging cohesins located near the bacterial surface are mechanically stronger than distal hanging cohesins, suggesting functional specialization within the scaffold, but the evolutionary origin of this mechanochemical divergence remained unknown. To address this, we applied ancestral sequence reconstruction (ASR) to trace the evolutionary pathway separating bridging and hanging cohesins: cohesin sequences were collected using BLASTp across multiple species, aligned with MUSCLE, and analyzed with RAxML under maximum-likelihood frameworks; divergence points were identified, and ancestral sequences were inferred with PAML to reconstruct the evolutionary trajectory leading to mechanochemical specialization. Structural modeling combined with steered molecular dynamics (SMD) simulations revealed that reconstructed ancestral cohesins retained mechanical strength comparable to bridging cohesins in A. cellulolyticus , providing new insight into the evolution of force resistance in cellulosomes.
Rosa et al. (2026) studied this question.