We have solved the high-resolution X-ray crystal structures of the CLZ domains of both CNGA1 and CNGA3. The proteins were expressed and purified from bacterial cell lysates and crystallized under vapour diffusion. Crystals of CNGA1#621-690 grew in space group P2 1 2 1 2 1 with three molecules in the asymmetric unit and diffracted to 2.14 Å. The structure of CNGA1#621-690 was solved using molecular replacement with the structure of HIV gp41 N-trimer pocket region 33 (3L36) as a search probe (Supplementary Table S1 ). The structure of CNGA3#626-672 in space group P12 1 1 was solved to 1.9 Å using molecular replacement with the structure of SARS virus S2 protein 34 (1ZVB) as a search probe (Supplementary Table S1 ).