This domain is about 150 amino acids in length found associated with Pfam:PF00595 in eukaryotes. It has a conserved GILD sequence motif. Family members have been found to be essential for cell polarity establishment and maintenance such as Par3 (partitioning defective) Swiss:Q8TEW0 and involved in conversion of histidine into ammonia (a crucial step for forming histamine in humans) such as Histidine ammonia lyase (HAL) Swiss:P42357. This N-terminal domain is found to mediate oligomerization critical for the membrane localization of Par-3. It is also found to possess a self-association capacity via a front-to-back mode in Par-3 and HAL proteins. However, unlike the Par-3 N-terminal domain which self-assembles into a left-handed helical filament, the HAL N-terminal domain does not tend to form a helical filament but rather self-assembles into circular oligomeric particles. This has been suggested to be likely due to the absence of equivalent charged residues that are essential for the longitudinal packing of the Par-3 N-terminal domain filament [1].

1: Structural insights into the intrinsic self-assembly of Par-3 N-terminal domain. Zhang Y, Wang W, Chen J, Zhang K, Gao F, Gao B, Zhang S, Dong M, Besenbacher F, Gong W, Zhang M, Sun F, Feng W; Structure. 2013;21:997-1006. PMID:23643951