This domain is found in SPECT1 (sporozoite microneme protein essential for cell traversal). It is formed of a four alpha-helix bundle with a 'hook'-like feature at one end. These helices in parallel or antiparallel alignment [1].

1: Structure of the essential Plasmodium host cell traversal protein SPECT1. Hamaoka BY, Ghosh P; PLoS One. 2014;9:e114685. PMID:25479287