Spore wall protein involved in the adhesion to host cells surface. Microsporidian spore adherence is an integral part of activation and host cell invasion which requires the extrusion at the spore apex of a very long and coiled structure, the polar tube, through which the sporoplasm is pushed to enter into the potential host cell. Synthesized during sporogony. Heparin-binding motifs (HBMs) are characterized by an XBBXBX or XBBBXXBX sequence, where X is any neutral amino acid and B is a positively charged basic amino acid, and are defined as the consensus sequence necessary for protein-heparin interactions. The HBM motif is involved in spore adherence to host cells.