The closely related estrogen-regulated trefoil proteins TFF1 and TFF3 have markedly different hydrodynamic properties, overall charge, and distribution of surface charge.

The human trefoil proteins TFF1 and TFF3 are expressed predominantly in the gastrointestinal tract. They are also expressed and regulated by estrogens in malignant breast epithelial cells. TFF1 and TFF3 are small cysteine-rich acidic secreted proteins of 60 and 59 amino acids with similar isoelectric points of 4.