High ratio infection of Mycoplasma hyorhinis in gastric tumor tissues suggests a possible association between mycoplasma infection and cancer. P37, an outer-membrane bacterial protein from Mycoplasma hyorhinis, increases neoplastic invasivity and metastasis and induces TNF-α secretion from human peripheral blood mononuclear cells (PBMC). To investigate the functional mechanism of P37, yeast two-hybrid system was used to isolate proteins interacted with P37 from a human placenta cDNA library. Among the 2.6×10⁶ transformant clones, one positive clone was obtained. Sequence analysis revealed that the clone is a cDNA fragment from Norpeg and encode a carboxy terminal protein. The interaction between P37 and Norpeg was further confirmed by ELISA and GST-Pull down assay. This result would be useful to study the function of P37 further.