Amyloid fibril aggregation: An insight into the underwater adhesion of barnacle cement

Barnacles robustly adhere themselves to diverse submarine substrates through a proteinaceous complex termed the "barnacle cement". Previous studies have indicated that certain peptides derived from some barnacle cement proteins can self-assemble into amyloid fibrils. In this study, we assessed the self-assembly behavior of a full-length 19 kDa cement protein from Balanus albicostatus (Balcp19k) in different buffers. Results of Thioflavin T binding assay, transmission electron microscopy, and Fourier transform infrared spectroscopy suggested that the bacterial recombinant Balcp19k was able to aggregate into typical amyloid fibrils. The time required for the self-assembly process was close to that required for the complete curing of barnacle cement complex. Moreover, the solubility of Balcp19k amyloid deposits in guanidine hydrochloride and urea was same as that of the cured cement. These results indicated the inherent self-assembling nature of Balcp19k, implying that the amyloid fibril formation plays a critical role in barnacle cement curing procedure and its insolubility. Our results should be conducive to understanding barnacle underwater adhesion mechanisms and have implications in the development of new-generation antifouling techniques and in the designing of novel wet adhesives for biomedical and technical applications.