Small-angle X-ray scattering reveals structural dynamics of the botulinum neurotoxin associating protein, nontoxic nonhemagglutinin

► Crystal and solution structures of NTNHA of type D botulinum TC were determined. ► The X-ray crystal structure and SAXS images showed a significant discrepancy. ► SAXS images of the M-TC and NTNHA indicate structural flexibility of NTNHA.