Binds lactose. May play a role in fruiting body formation. Homotetramer. Oligomerization is required for carbohydrate binding. Detected in extracellular matrix, cell wall and cytoplasmic membrane-bound bodies. Most abundant in fruiting bodies. Very low levels of expression in asexual vegetative mycelia. Most abundant prior to premeiotic S-phase, remains high from karyogamy to early pachytene, declines drastically by late pachytene and diplotene, and is undetectable by sterigma stage. Repressed by continuous light. Was originally thought to be an endonuclease subunit.