The invention relates to constructs comprising a transmembrane protein pore subunit and a nucleic acid handling enzyme. The pore subunit is covalently attached to the enzyme such that both the subunit and enzyme retain their activity. The constructs can be used to generate transmembrane protein pores having a nucleic acid handling enzyme attached thereto. Such pores are particularly useful for sequencing nucleic acids. The enzyme handles the nucleic acid in such a way that the pore can detect its component nucleotides by stochastic sensing.