To obtain a new protein consisting of a protein having a specific amino acid sequence, capable of binding with an ALG-2 protein associated with an apoptosis or a cell cycle adjustment and an inhibitor of which is useful for the diagnosis, treatment, etc., of the apoptosis, cancer, etc.

This apoptosis-associated antigen consists of amino acid sequences described as formulae I, II or III and can bind with a human origin ALG-2 protein associated with the apoptosis or a cell cycle adjustment, and used as a screening of inhibitors thereof, etc., since a compound inhibiting the binding of the protein with the ALG-2 protein is useful for an elucidation of the molecular mechanism of the apoptosis, cancer, etc., and the diagnosis and treatment of cancer, etc. The protein is obtained by adding a solubilized buffer cooled with ice to Jurkat cells, completely dissolving cells by a vigorous agitation, subjecting the cell solution to an ultra centrifuge, separating a supernatant, passing the same through a column fixed with an anti-ALG-2 antibody, and eluting the bound immuno-precipitated material with an eluting buffer.