Connective tissue growth factor (CTGF) is a 349-residue mosaic protein that contains four structural modules implicated in protein-protein interactions. To address the functionality of residues 247-349 (containing module 4 alone), this region of CTGF was produced as a maltose binding protein (MBP) fusion protein in E. coli. After removal of MBP, recombinant CTGF commenced at Glu 247 , was of M r 10 000, was immunoreactive with anti-CTGF [247][248][249][250][251][252][253][254][255][256][257][258][259][260], bound strongly to heparin, and promoted dose-dependent adhesion of fibroblasts, myofibroblasts, endothelial cells, and epithelial cells. An 8 kDa presumptive C-terminally truncated form of CTGF commencing at Glu 247 also promoted cell adhesion. CTGFmediated cell adhesion was abolished by heparin or EDTA. These data demonstrate the presence of heparinbinding and cell-adhesion motifs within the C-terminal 103 residues of CTGF and show that CTGF-mediated cell adhesion is heparin-and divalent cation-dependent. Thus, CTGF isoforms comprising essentially module 4 are intrinsically functional in the absence of the other constituent modules of CTGF.