Domain found in small family of bacterial secreted proteins with no known function. Also found in Paramecium bursaria chlorella virus 1. This domain is short and found in one or two copies. The domain has a conserved HH motif that may be functionally important. This domain belongs to the ferritin superfamily. It contains two sequence similar repeats each of which is composed of two alpha helices.

1: New Knowledge from Old: In silico discovery of novel protein domains in Streptomyces coelicolor. Yeats C, Bentley S, Bateman A; BMC Microbiol 2003;3:3-3. PMID:12625841