Although botulinum neurotoxin serotype A (BoNT/A) products are common treatments for various disorders， there is only one commercial BoNT product， whose low potency， likely stemming from low affinity toward its human receptor synaptotagmin 2 (hSyt2)， has limited its therapeutic usefulness. We express and characterize two full-length recombinant BoNT1 proteins containing designed mutations E1191M/S1199Y (rBoNT1) and E1191Q/S1199W (rBoNT1) that enhance binding to hSyt2. In preclinical models including human-induced pluripotent stem cell neurons and a humanized transgenic mouse， this increased hSyt2 affinity results in high potency， comparable to that of BoNT/A. Last， we solve the cocrystal structure of rBoNT1 in complex with peptides of hSyt2 and its homolog hSyt1. We demonstrate that neuronal surface receptor binding limits the clinical efficacy of unmodified BoNT and that modified BoNT proteins have promising clinical potential.