Binding Sites on PTP1B Enzyme (image) Cold Spring Harbor Laboratory Caption The PTP1B inhibitor MSI-1436 (trodusquemine) binds at two sites on the enzyme. The principal allosteric site, a weaker alternate site, and the previously recognized main, or catalytic, binding site are shown in this rendering. Credit Tonks lab/Cold Spring Harbor Laboratory Usage Restrictions give credit please Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.