Surface layer proteins (SLPs) of lactobacillus bacteria have some structural regions responsible for adhesion to the intestinal epithelium. To identify the SLP and the smallest domain within the protein that is responsible for the adhesion of the bacterium to the intestinal epithelium, L. plantarum strain CGMCC1258 was investigated in this study. Using bioinformatics and molecular techniques, we first identified and purified a novel protein, integral membrane protein-2 (IMP-2, 33-45 kDa) responsible for adhesion to gastric mucin. Truncated forms of IMP-2 were then constructed and expressed, and the amino acids from 515 to 575 (designated micro IMP, MIMP) was identified as the smallest domain responsible for adhesion to gastric mucin. Competing assay was performed, which further confirmed the ability of MIMP to compete with enteroinvasive E. coli and enteropathogenic E. coli to adhere to cells of a normal colon cell line, NCM460. Furthermore, MIMP could maturate dendritic cells. These findings set a foundation for further investigation on the role of MIMP in the treatment and prevention of inflammation-related diseases of the intestine.