Two-Species Active Transport along Cylindrical Biofilaments is Limited by Emergent Topological Hindrance

Abstract

Active motion of molecules along filamentous structures is a crucial feature of cell biology and is often modeled with the paradigmatic asymmetric simple exclusion process. Motivated by recent experimental studies that have addressed the stepping behavior of kinesins on microtubules, we investigate a lattice gas model for simultaneous transport of two species of active particles on a cylinder. The species are distinguished by their different gaits: While the first species moves straight ahead, the second follows a helical path. We show that the collective properties of such systems critically differ from those of one-species transport in a way that cannot be accounted for by standard models. This is most evident in a jamming transition far below full occupation, as well as in non-equilibrium pattern formation. The altered behavior arises because -unlike the case in single-species transport -any given position may be targeted by two particles from different directions at the same time. However, a particle can leave a given position only in one direction. This simple change in connectivity significantly amplifies the impact of steric interactions and thus becomes a key determinant of mixed species transport. We computationally characterize this type of hindrance and develop a comprehensive theory for collective two-species transport along a cylinder. Our observations show high robustness against model extensions that account for additional biomolecular features and demonstrate that even small fractions of a second species can significantly alter transport. This suggests that our analysis is also relevant in a biological context. * P.W. and E.R. contributed equally to this work. † frey@lmu.de arXiv:1807.02410v1 [cond-mat.stat-mech]

The 2020 motile active matter roadmap

“…For increased realism, we may need to move beyond our current representation of filaments as having a backbone of vanishing thickness. This will be required for modelling systems where the motors follow helical paths on the microtubule surface [217]. Similarly, it is desirable to represent the natural twist of actin filaments, a source of chirality in actin networks that is of biological importance.…”

Totally asymmetric simple exclusion process with particle annihilation

“…This, for example, happens in transport processes inside the narrow axonal regions of neurons where the space is further crowded due to the presence of a large number of actin filaments, stalled motor proteins, etc [21]. The question as to how the dynamics of motor proteins is altered in a crowded environment has led to a large number of studies with many of those focusing on the dwell time, run length characteristics, etc, of motor proteins [22][23][24][25]. In an earlier work [25], Conway et al investigated cargo transport along microtubles using a quantum dot cargo that can associate or dissociate motor molecules as it translocates.…”

Dynein-Inspired Multilane Exclusion Process with Open Boundary Conditions

“…Interestingly, kinesins and dyneins show small but discernible sidewise fluctuations on the microtubule tracks consisting of multiple protofilaments [10][11][12][13][14]. Thus, modeling of kinesin dynamics with the ability to switch lanes has been considered [15], whereas the emergent behavior due to incorporating multi-lane dynamics of dynein motors along with variable steps sizes is as yet unknown. Most of the theoretical modeling of dynein motors has been restricted to the analysis of single-molecule dynamics [16,17], or of multi-particle dynamics on a single protofilament track [18,19].…”