Requirement of anionic groups for the mitogenicity of a fungal mitogen, vesiculogen.

Active site(s) of a B-cell mitogen, vesiculogen, was investigated by means of chemical and enzymic modifications. Vesiculogen is a non-dialyzable fraction of a hot water extract from a fungus, Peziza vesiculosa (Yadomae et al, Microbiol. Immunol. 23, 997 (1979], and was composed of protein (approximately 60%), carbohydrate (approximately 30%), and a small amount of amino sugar, uronic acid, phosphate, and lipid. The mitogenicity was not affected by periodate oxidation, N-acylation, defatting treatment, destruction of the three dimensional structure, protease digestion, nuclease digestion, N-bromosuccinimide treatment, and beta-mercaptoethanol treatment. However, the mitogenicity was decreased by a modification of carboxyl groups, such as 1-ethyl-3(3-dimethylamino propyl)-carbodiimide or dicyclohexylcarbodiimide treatment. Vesiculogen contains a large amount of acidic amino acids. These results suggest that the mitogenicity of vesiculogen is due to the presence of anionic groups, such as aspartic acid and glutamic acid, and that the mitogenic substance is a novel, heat stable polyanionic B-cell activator obtained from Ascomycotina.