Control of electrostatic interactions between F-actin and genetically modified lysozyme in aqueous media

Lori K. Sanders, Wujing Xian, Camilo Guáqueta, Michael J. Strohman, Chuck R. Vrasich, Erik Luijten*, Gerard C L Wong

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

48 Scopus citations

Abstract

The aim for deterministic control of the interactions between macroions in aqueous media has motivated widespread experimental and theoretical work. Although it has been well established that like-charged macromolecules can aggregate under the influence of oppositely charged condensing agents, the specific conditions for the stability of such aggregates can only be determined empirically. We examine these conditions, which involve an interplay of electrostatic and osmotic effects, by using a well defined model system composed of F-actin, an anionic rod-like polyelectrolyte, and lysozyme, a cationic globular protein with a charge that can be genetically modified. The structure and stability of actin-lysozyme complexes for different lysozyme charge mutants and salt concentrations are examined by using synchrotron x-ray scattering and molecular dynamics simulations. We provide evidence that supports a structural transition from columnar arrangements of F-actin held together by arrays of lysozyme at the threefold interstitial sites of the actin sublattice to marginally stable complexes in which lysozyme resides at twofold bridging sites between actin. The reduced stability arises from strongly reduced partitioning of salt between the complex and the surrounding solution. Changes in the stability of actin-lysozyme complexes are of biomedical interest because their formation has been reported to contribute to the persistence of airway infections in cystic fibrosis by sequestering antimicrobials such as lysozyme. We present x-ray microscopy results that argue for the existence of actin-lysozyme complexes in cystic fibrosis sputum and demonstrate that, for a wide range of salt conditions, charge-reduced lysozyme is not sequestered in ordered complexes while retaining its bacterial killing activity.

Original languageEnglish (US)
Pages (from-to)15994-15999
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume104
Issue number41
DOIs
StatePublished - Oct 9 2007

Keywords

  • Antimicrobial
  • Cystic fibrosis
  • Self-assembly
  • Small-angle x-ray scattering
  • x-ray microscopy

ASJC Scopus subject areas

  • General

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