Coarse-grained model of tropoelastin self-assembly into nascent fibrils

A Tarakanova; J Ozsvar; A S Weiss; M J Buehler

doi:10.1016/j.mtbio.2019.100016

Coarse-grained model of tropoelastin self-assembly into nascent fibrils

Mater Today Bio. 2019 Jun 18:3:100016. doi: 10.1016/j.mtbio.2019.100016. eCollection 2019 Jun.

Authors

A Tarakanova^{1

2}, J Ozsvar^{3

4}, A S Weiss^{3

4

5

6}, M J Buehler¹

Affiliations

¹ Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
² Department of Mechanical Engineering and Department of Biomedical Engineering, University of Connecticut, Storrs, CT, USA.
³ School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW, Australia.
⁴ Charles Perkins Centre, The University of Sydney, Sydney, NSW, Australia.
⁵ Bosch Institute, The University of Sydney, Sydney, NSW, Australia.
⁶ Sydney Nano Institute, The University of Sydney, Sydney, NSW, Australia.

Abstract

Elastin is the dominant building block of elastic fibers that impart structural integrity and elasticity to a range of important tissues, including the lungs, blood vessels, and skin. The elastic fiber assembly process begins with a coacervation stage where tropoelastin monomers reversibly self-assemble into coacervate aggregates that consist of multiple molecules. In this paper, an atomistically based coarse-grained model of tropoelastin assembly is developed. Using the previously determined atomistic structure of tropoelastin, the precursor molecule to elastic fibers, as the basis for coarse-graining, the atomistic model is mapped to a MARTINI-based coarse-grained framework to account for chemical details of protein-protein interactions, coupled to an elastic network model to stabilize the structure. We find that self-assembly of monomers generates up to ∼70 nm of dense aggregates that are distinct at different temperatures, displaying high temperature sensitivity. Resulting assembled structures exhibit a combination of fibrillar and globular substructures within the bulk aggregates. The results suggest that the coalescence of tropoelastin assemblies into higher order structures may be reinforced in the initial stages of coacervation by directed assembly, supporting the experimentally observed presence of heterogeneous cross-linking. Self-assembly of tropoelastin is driven by interactions of specific hydrophobic domains and the reordering of water molecules in the system. Domain pair orientation analysis throughout the self-assembly process at different temperatures suggests coacervation is a driving force to orient domains for heterogeneous downstream cross-linking. The model provides a framework to characterize macromolecular self-assembly for elastin, and the formulation could easily be adapted to similar assembly systems.

Keywords: Coacervation; Elastic network model; Elastin; Hierarchical; MARTINI; Multiscale modeling.

Grants and funding

U01 EB014976/EB/NIBIB NIH HHS/United States