Targeted Modulation of Tropoelastin Structure and Assembly.

Giselle C Yeo,Steven G Wise,Anthony S Weiss,Clair Baldock,Clair Baldock

doi:10.1021/acsbiomaterials.6b00564

Abstract

Tropoelastin, as the monomer unit of elastin, assembles into elastic fibers that impart strength and resilience to elastic tissues. Tropoelastin is also widely used to manufacture versatile materials with specific mechanical and biological properties. The assembly of tropoelastin into elastic fibers or biomaterials is crucially influenced by key submolecular regions and specific residues within these domains. In this work, we identify the functional contributions of two rarely occurring negatively charged residues, glutamate 345 in domain 19 and glutamate 414 in domain 21, in jointly maintaining the native conformation of the tropoelastin hinge, bridge and foot regions. Alanine substitution of E345 and/or E414 variably alters the positioning and interactive accessibility of these regions, as illustrated by nanostructural studies and detected by antibody and cell probes. These structural changes are associated with a lower propensity for monomer coacervation, cross-linking into morphologically and functionally atypical hydrogels, and markedly impaired and abnormal elastic fiber formation. Our work indicates the crucial significance of both E345 and E414 residues in modulating specific local structure and higher-order assembly of human tropoelastin.

Highlights

Tropoelastin is the monomer unit of elastin, the main component of elastic fibers in the extracellular matrix that confer strength and resilience to elastic tissues such as skin, lungs, and vasculature.[1]
We aim to investigate the significance of these negatively charged residues by constructing tropoelastin variants with mutations at one or both sites: E345A, where the E345 residue has been replaced with an alanine; E414A, where the E414 residue has been replaced with an alanine; and E345A+E414A, where both E345 and E414 have been substituted by alanines (Figure 1)
These results suggest central and C-terminal conformational changes associated with mutation/s at E345 or E414, which encompass but are not confined to the expected locations of these sites, and which are not linked to global changes in protein secondary structure composition

Summary

Introduction

Tropoelastin is the monomer unit of elastin, the main component of elastic fibers in the extracellular matrix that confer strength and resilience to elastic tissues such as skin, lungs, and vasculature.[1]. Tropoelastin assembly into higher-order structures is strongly influenced at each stage by distinct contributions from its submolecular regions. Previous studies have identified the pivotal roles of the N-terminal coil,[3] the central hinge and bridge,[4−7] and the C-terminal foot[8,9] regions during the coacervation, microfibrillar deposition and cross-linking stages of elastic fiber formation Within these regions, there are specific residues that directly participate in intra- and intermolecular contacts,[10−12] or maintain the local and global conformation essential for functional assembly.[3,6] Such residues potentially modulate tropoelastin behavior via charge-based interactions

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Discussion

Conclusion