Condensation Agents Determine the Temperature–Pressure Stability of F‐Actin Bundles

Abstract

Biological cells provide al arge variety of rodlike filaments,i ncluding filamentous actin (F-actin), which can form meshworks and bundles.One key question remaining in the characterization of such network structures revolves around the temperature and pressure stabilities of these architectures as aw ay to understand why cells actively use proteins for forming them. The packingproperties of F-actin in fascin-and Mg 2+ -induced bundles are compared, and significantly different pressure-temperature stabilities are observed because of marked differences in their nature of interaction, solvation, and packinge fficiency.M oreover,d ifferences are observed in their morphologies and disintegration scenarios. The pressure-induced dissociation of the actin bundles is reminiscent of as ingle unbinding transition as observed in other soft elastic manifolds.

High pressure effects on the structural functionality of condensed globular-protein matrices

“…Thus, P-T diagrams illustrate the regimes where a loss of protein native structure or enzymatic activity occurs, and document that pressure is able to stabilize proteins against heat denaturation in a restricted range of temperatures [19]. The ellipsoidal shape of the P-T diagram has been confirmed for carbonylhaemoglobin and ovalbumin, however, the exact phase diagram in the temperaturepressure plane is still unknown for several proteins, particularly below 0 • C. Recently, temperature-pressure perturbations have been used to explore the energy landscapes of various conformation states of globular proteins including filamentous actin that determine several biological processes and debilitating diseases [46,20].…”

Regulation of Actin Bundle Mechanics and Structure by Intracellular Environmental Factors

“…They demonstrated that the stiffness, elasticity, and non-linear force response of the actin network increase with increasing concentration of Mg 2+ (≥10mM) ( Table 1 ) [ 41 ]. Cation binding at discrete sites along actin filaments can lead to bundle formation and promote modulations to bundle structural properties, such as helical twist [ 16 , 25 , 41 , 58 , 59 ]. Small-angle x-ray scattering (SAXS) showed that actin filaments condensed into bundles display an over twisting of filaments within the bundles [ 25 ].…”