Title:Calcium and Sodium-mediated Dynamic Assembly of Intermediate
Filament-like Protein FilP
Volume: 30
Issue: 2
Author(s): Caihong Fu, Shanshan Zhang, Fan Yang, Ximing Chen*Xiuxia Sun*
Affiliation:
- Key Laboratory of Desert & Desertification, Cold & Arid Regions
Environmental & Engineering Research Institute, Chinese Academy of Sciences, Lanzhou University, Lanzhou, 730000,
China
- School of Pharmacy, Lanzhou University, Lanzhou, 730000, China
Keywords:
FilP, cytoskeletal, assembly, light scattering, polymerization, Streptomyces coelicolor.
Abstract:
Background: Cytoskeletal elements play key roles in cell morphology, cell division, cell
mobility, and DNA partitioning in all domains of life. The IF-like protein FilP was discovered in
Streptomyces coelicolor, and it was found to perform a structurally important cytoskeletal role by
providing direct mechanical support for the cells.
Objective: This work investigated the factors influencing FilP polymerization under a variety of
conditions.
Methods: DLS technique was applied to real-time monitor the in vitro assembly process of
Streptomyces coelicolor FilP.
Results: The presence of small amounts of divalent cations, such as CaCl2 or MgCl2, enhanced the
polymerization of FilP, while higher amounts suppressed its polymerization. Moreover, high
concentrations of NaCl, KCl, NH4Cl, and KNO3 both suppressed the polymerization of FilP. EDTA
was found to have a very prohibitive effect on FilP polymerization, and even the following addition of
Ca2+ could not initiate the assembly of FilP. FilP polymerized under a range of pHs ranging from pH
6 to pH 8, while the polymerization degree was sensitive to pH. FilP formed network-like, striated
filaments at neutral pH, while the filaments became more disordered or loosely packed at pH 8 and
pH 6, respectively.
Conclusion: FilP assembly is calcium-mediated. Ca2+ is not only required for FilP polymerization,
but also required for FilP to maintain the higher-order polymer structure. The accelerative effect of
Ca2+ and the suppressive effect of Na+ persisted under a wide range of conditions, suggesting that FilP
might use calcium and sodium ions as a general mechanism to mediate its polymerization process.