The present invention relates to a novel protein inhibiting .beta. amyloid aggregation and a strain producing the protein, more precisely, to a novel protein inhibiting .beta. amyloid aggregation, a gene coding the protein, a Streptomyces sp. strain producing the protein and a therapeutic agent for neurodegenerative disorders containing the protein as an effective ingredient. The therapeutic agent of the present invention containing the protein inhibiting .beta. amyloid aggregation as an effective ingredient can be effectively used for the prevention and the treatment of neurodegenerative disorders like Alzheimer's disease.