The invention relates to bacterial cell surface display of post-translationally modified heterologous proteins. Provided is an isolated nucleic acid construct encoding a proteinaceous substance comprising, from the N-terminus to the C-terminus, at least (a) an N-terminal a lantibiotic leader sequence; (b) an amino acid sequence of interest to be post-translationally modified to a dehydroresidue- or thioether-bridge containing polypeptide; (c) a hydrophilic cell-wall spanning domain; (d) a sortase recognition motif; (e) a hydrophobic membrane spanning domain and (f) a C-terminal charged membrane anchoring domain. Also provided is a Gram-positive host cell expressing the construct, as well as a library of host cells.