A method for displaying a polypeptide of interest on a cell surface, the method comprising: a. providing a host cell comprising a first nucleic acid encoding an engineered protein, wherein the host cell expresses a recombinant biotin protein ligase covalently fused to a first secretion leader peptide, wherein the host cell is a eukaryotic host cell, wherein the first secretion leader peptide is fused to the N-terminus of the recombinant biotin protein ligase, wherein the host cell has avidin, streptavidin or variant thereof capable of binding biotin, coupled to the extracellular side of the host cell surface, wherein the engineered protein comprises a polypeptide of interest covalently fused to a second secretion leader peptide, wherein the second secretion leader peptide is at the N-terminus of the engineered protein, wherein the first secretion leader peptide and the second secretion leader peptide is a peptide that directs proteins to the eukaryotic secretory pathway, wherein the engineered protein comprises a first biotin acceptor peptide covalently fused to either the N-terminus or C-terminus of the polypeptide of interest, wherein the first biotin acceptor peptide contains a lysine residue, wherein the ε-amino group of the lysine residue is capable of forming a post-translational amide-linkage to the carboxyl group of biotin when catalyzed by the recombinant biotin protein ligase, wherein the recombinant biotin protein ligase is selected from the group of SEQ ID NOs 1-10 and variants thereof capable of catalyzing the post-translational linkage between biotin and the first biotin acceptor peptide, and b. expressing the engineered protein, wherein expression of the engineered protein results in intracellular coupling of a biotin moiety covalently to the first biotin acceptor peptide catalyzed by the recombinant biotin protein ligase within the host cell secretory pathway and in secretion of the biotinylated engineered protein without the secretion leader peptide from the cell surface into the extracellular medium so that the biotin moiety of the engineered protein binds noncovalently and specifically to the avidin, streptavidin, or variant thereof capable of binding biotin, thereby displaying the polypeptide of interest on the extracellular side of the host cell surface. a. providing a host cell comprising a first nucleic acid encoding an engineered protein, wherein the host cell expresses a recombinant biotin protein ligase covalently fused to a first secretion leader peptide, wherein the host cell is a eukaryotic host cell, wherein the first secretion leader peptide is fused to the N-terminus of the recombinant biotin protein ligase, wherein the host cell has avidin, streptavidin or variant thereof capable of binding biotin, coupled to the extracellular side of the host cell surface, wherein the engineered protein comprises a polypeptide of interest covalently fused to a second secretion leader peptide, wherein the second secretion leader peptide is at the N-terminus of the engineered protein, wherein the first secretion leader peptide and the second secretion leader peptide is a peptide that directs proteins to the eukaryotic secretory pathway, wherein the engineered protein comprises a first biotin acceptor peptide covalently fused to either the N-terminus or C-terminus of the polypeptide of interest, wherein the first biotin acceptor peptide contains a lysine residue, wherein the ε-amino group of the lysine residue is capable of forming a post-translational amide-linkage to the carboxyl group of biotin when catalyzed by the recombinant biotin protein ligase, wherein the recombinant biotin protein ligase is selected from the group of SEQ ID NOs 1-10 and variants thereof capable of catalyzing the post-translational linkage between biotin and the first biotin acceptor peptide, and b. expressing the engineered protein, wherein expression of the engineered protein results in intracellular coupling of a biotin moiety covalently to the first biotin acceptor peptide catalyzed by the recombinant biotin protein ligase within the host cell secretory pathway and in secretion of the biotinylated engineered protein without the secretion leader peptide from the cell surface into the extracellular medium so that the biotin moiety of the engineered protein binds noncovalently and specifically to the avidin, streptavidin, or variant thereof capable of binding biotin, thereby displaying the polypeptide of interest on the extracellular side of the host cell surface.