Disulfide bonding arrangements in active forms of the somatomedin B domain of human vitronectin

The N-terminal cysteine-rich somatomedin B (SMB) domain of the human glycoprotien vitronectin contains the high-affinity binding sites for plasminogen activator inhibitor-1(PAI-1) and the urokinase receptor (uPAR). The studies demonstrate that the three dimensional structure of the SMB domain is extremely compact and that the disulfide bonds are packed in the center of the domain forming a covalently bonded core.