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In-silico Molecular Investigation of Caloubater crescentus Bioadhesive Proteins

Authors :

Yeganeh Kayalha¹ Maryam Azimzadeh Irani²

1- دانشگاه شهید بهشتی 2- Faculty of Life Sciences and Biotechnology Shahid Beheshti University

Keywords :

Holdfast،Bacterial bioadhesive،Protein structure،Immunoinformatics

Abstract :

Caulobacter crescentus, also known as Caulobacter vibrioides, produces a specialized adhesive structure, the holdfast—a polysaccharide-rich matrix located at the stalk tip that enables strong surface attachment. This structure allows strong attachment through its potent adhesive properties. The “holdfast” in this bacterium is believed to have the highest tensile strength of any known biological adhesive. Three major membrane-associated proteins—HfaA, HfaB, and HfaD—are anchoring components of the holdfast, which enhances its interaction with polysaccharides and thereby reinforces stable surface attachment. In this study, Bioinformatics analyses were performed. BLAST and multiple sequence alignment revealed conserved regions across the proteins. At the same time, phylogenetic analysis indicated a close relationship between Cp19k barnacle’s adhesive protein and HfaA, with HfaB forming a more distant group with Cp20k barnacle’s adhesive protein variants, which, along with Cp19k, are bioadhesive proteins commonly found in barnacles. Structural modeling using AlphaFold2 showed that HfaA had moderate confidence with flexible regions, in the central and C-terminal domains (pLDDT ~64). HfaB displayed greater stability (pLDDT >75), while HfaD achieved the highest confidence scores (pLDDT >91), with consistent folding across all models. The Epitope prediction using DiscoTope identified multiple B-cell epitope regions in HfaA and HfaB, but limited immunogenicity in HfaD. AlphaFold-Multimer modeling of the protein complex yielded low inter-chain confidence (ipTM <0.20), suggesting weak subunit interaction. These results may lead to the development of biocompatible bioadhesive materials for medical and industrial usage.