Characterizing key proteins that contribute to barnacle adhesion

Abstract

Barnacles can tenaciously adhere to almost any surface. To stick to a surface, glues are released and form an adhesive bond between the surface and the barnacle's base plate. The predomi-nantly proteinaceous glue is composed of approximately a dozen proteins, which serve various roles in the adhesion process. Here, protein characterization was paired with whole organism measures of adhesive strength. Barnacle adhesive strength was quantified in shear using a digital force gauge. The goal was to identify key proteins that contribute to the adhesive strength. Uncured glue from each barnacle was extracted and separated using SDS-PAGE. Abundance of each individual protein was quantified using image analysis software. Correlation analysis revealed a significant positive relationship between the abundance of a 28-kDa glue protein and adhesive strength, i.e. barnacles that expressed more of this particular protein adhered more strongly. This relationship suggests that the 28-kDa protein plays a vital role in adhesion. Subsequent analyses showed that this protein is phosphorylated with a pI of approximately 6.3. Phosphorylated proteins, which possess sticky characteristics due to negatively-charged phosphate groups, may play a role in adhesive functionality of the glue. Understanding what components and characteristics contribute to the glue's effectiveness underwater has many practical implications, including antifouling and biomedical adhesives. The authors gratefully acknowledge funding by ONR, N00014-14-1-0491.