Differential Sequence Charge-clustering and Mixing-ratio Affect Stability and Dynamics of Heterotypic Peptide Condensates

Abstract

Phase separation has emerged as a central mechanism cell utilizes to organize its material components and are extremely important in tuning various biological regulations. However, such condensates in cellular media is often very much heterogeneous in nature in terms of proteins and even polynucleotides presence in different concentrations. Present study explores stability and dynamics of heterotypic coacervates formed by polyampholyte binary peptides having differential charge-clustering limits. Systematic increase in differential charge-clustering in peptide pairs tunes the origin of heterogeneity and shows an enhanced stability of droplet than homogeneous ones with same average charge clustering of the two peptide pairs. In addition, stability of the condensate phase enhances linearly with the increase of high charge-clustering polymers in the system. Peptides with higher charge-clustering are 3-4 times slower diffusive within condensate phase than the lower charge-clustering ones due to heterogeneity in structural morphology of droplets, that too diminish as one lowers the difference of charge-clustering among sequence pairs forming the condensate. Coupled to the differential diffusivity of the polymers in condensates, droplet diffusion is nearly 7-35 times lower than bulk depending upon the mixing ratios of the polymers and variable sequence charge-clustering. Condensates with mild heterogeneity have shown an enhanced arrestation than the most heterogeneous ones originating from complementarity and better packing probed by energetics in the condensate. This study quantifies fundamental microscopic properties of heterotypic condensates formed through long-range electrostatic forces and particularly how they can be modulated by the differential charge-pattern in sequences and mixing fraction systematically.