Part:BBa_K4395005

SpyTag is one of the two components of the SpyTag/SpyCatcher tagging system. This system is a split-in-two of the immunoglobulin-like collagen adhesion domain of Streptococcus pyogenes denoted CnaB2, which mediates cell-cell homophilic binding independent of Ca2+ [1-2]. CnaB2 is characterized by an internal isopeptide bond between residue Lys31 and residue Asp117. When split in two, one of which containing Lys31 and another containing Asp117, they associate and spontaneously form the isopeptide bond, thus join together [1]. Various enzymes, such as cyclized phytase, are able to mediate the cyclization. And the C-terminal fragment is thus denoted SpyTag. The usage of the SpyTag/SpyCatcher tagging system has been previous established in enzyme immobilization in large-sacle industrial applications to minimize the steric hindrance of enzyme activity [3]. It was also proven to be able to increase enzyme thermostability by cyclizing them [4]. In such two cases, the two components of the tagging system were fused either on both ends of a protein or on proteins and matrices.

References: [1] Long Li, Jacob O. Fierer, et al. Structural Analysis and Optimization of the Covalent Association between SpyCatcher and a Peptide Tag J Mol Biol. 2014 January 23; 426(2): 309–317 [2] Vladislav V. Kiselyov, Vladimir Berezin, et al. The First Immunoglobulin-like Neural Cell Adhesion Molecule (NCAM) Domain Is Involved in Double-reciprocal Interaction with the Second Immunoglobulin-like NCAM Domain and in Heparin Binding [3] Xin Gao, Cancan Wei, et al. Directional immobilization of D-allulose 3-epimerase using SpyTag/SpyCatcher strategy as a robust biocatalyst for synthesizing D-allulose [4] Xiao-Bao Suna, Jia-Wen Caoa,b, et al. SpyTag/SpyCatcher molecular cyclization confers protein stability and resilience to aggregation