Proteogenomic Characterization of the Cement and Adhesive Gland of the Pelagic Gooseneck Barnacle Lepas anatifera.

Dany Domínguez-Pérez,Daniela Almeida,Josef Wissing,Alexandre Campos,Vitor Vasconcelos,Agostinho Antunes,Lothar Jänsch,Luís Filipe Castro,Isabel Cunha,André M Machado

doi:10.3390/ijms22073370

Abstract

We focus on the stalked goose barnacle L. anatifera adhesive system, an opportunistic less selective species for the substrate, found attached to a variety of floating objects at seas. Adhesion is an adaptative character in barnacles, ensuring adequate positioning in the habitat for feeding and reproduction. The protein composition of the cement multicomplex and adhesive gland was quantitatively studied using shotgun proteomic analysis. Overall, 11,795 peptide sequences were identified in the gland and 2206 in the cement, clustered in 1689 and 217 proteinGroups, respectively. Cement specific adhesive proteins (CPs), proteases, protease inhibitors, cuticular and structural proteins, chemical cues, and many unannotated proteins were found, among others. In the cement, CPs were the most abundant (80.5%), being the bulk proteins CP100k and -52k the most expressed of all, and CP43k-like the most expressed interfacial protein. Unannotated proteins comprised 4.7% of the cement proteome, ranking several of them among the most highly expressed. Eight of these proteins showed similar physicochemical properties and amino acid composition to known CPs and classified through Principal Components Analysis (PCA) as new CPs. The importance of PCA on the identification of unannotated non-conserved adhesive proteins, whose selective pressure is on their relative amino acid abundance, was demonstrated.

Highlights

Goose barnacles are filter-feeding marine crustaceans that live attached by the stalk to a fixed hard substrate, or to floating objects, by means of an adhesive secretion
The core of the secretion is composed by cohesive hydrophobic proteins named “bulk proteins”, since they are the most abundant, while interfacial proteins are less abundant hydrophilic proteins making the outside boundary of the cement complex
Six barnacle specific cement proteins (CPs) have been identified to two bulk proteins, CP52k and -100k, and four interfacial proteins, CP19k, -20k, -43k, and -68k [11], where the numbers correspond to the approximate molecular weight in kilo Daltons

Summary

Introduction

Goose barnacles are filter-feeding marine crustaceans that live attached by the stalk to a fixed hard substrate, or to floating objects, by means of an adhesive secretion. Six barnacle specific cement proteins (CPs) have been identified to two bulk proteins, CP52k and -100k, and four interfacial proteins, CP19k, -20k, -43k, and -68k [11], where the numbers correspond to the approximate molecular weight in kilo Daltons. In some cases (e.g., CP19k and CP20k; surface coupling proteins) they may have similar weight and feature very different physicochemical properties and amino acid relative abundance. In Pollicipes pollicipes several putative CPs were recently reported in the cement, with a variety of molecular weights [15] These barnacle CPs did not show any homology with other marine adhesive proteins [11,12], or other proteins at all, possessing no identifiable protein domains, being in some cases structurally very disordered, and that could not be named in the previously defined CP’s nomenclature

Methods

Results

Conclusion