During thymocyte development, may play a role in the regulation of apoptosis (By similarity). GTPase which exhibits a higher affinity for GDP than for GTP (By similarity). May interact (via IQ domain) with calmodulin/CALM1 only in the absence of Ca(2+) (By similarity). Interacts with BAX, but not with other Bcl-2 family members (By similarity). Primarily expressed in spleen, thymus, heart, lung and intestine and, at lower levels, in liver, kidney, stomach and muscle (PubMed:12031988). In the spleen, expressed in periarteriolar lymphatic sheets (PubMed:12031988). In the thymus, detected in the medulla (PubMed:12031988). Phosphorylated at very low levels in resting splenocytes. Rapidly and transiently phosphorylated in response to splenocyte activation. Belongs to the TRAFAC class TrmE-Era-EngA-EngB-Septin-like GTPase superfamily. AIG1/Toc34/Toc159-like paraseptin GTPase family. IAN subfamily.