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Defining the metal specificity of a multifunctional biofilm adhesion protein
Author(s) -
Chaton Catherine T.,
Herr Andrew B.
Publication year - 2017
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.3232
Subject(s) - biofilm , adhesion , chemistry , computational biology , biophysics , microbiology and biotechnology , biochemistry , biology , bacteria , genetics , organic chemistry
The accumulation associated protein (Aap) of Staphylococcus epidermidis mediates intercellular adhesion events necessary for biofilm growth. This process depends upon Zn 2+ ‐induced self‐assembly of G5 domains within the B‐repeat region of the protein, forming anti‐parallel, intertwined protein “ropes” between cells. Pleomorphism in the Zn 2+ ‐coordinating residues was observed in previously solved crystal structures, suggesting that the metal binding site might accommodate other transition metals and thereby support dimerization. By use of carefully selected buffer systems and a specialized approach to analyze sedimentation velocity analytical ultracentrifugation data, we were able to analyze low‐affinity metal binding events in solution. Our data show that both Zn 2+ and Cu 2+ support B‐repeat assembly, whereas Mn 2+ , Co 2+ , and Ni 2+ bind to Aap but do not support self‐association. As the number of G5 domains are increased in longer B‐repeat constructs, the total concentration of metal required for dimerization decreases and the transition between monomer and dimer becomes more abrupt. These characteristics allow Aap to function as an environmental sensor that regulates biofilm formation in response to local concentrations of Zn 2+ and Cu 2+ , both of which are implicated in immune cell activity.